The use of polyethylene pipes in the national economy and household sphere is due to their physical properties and high functional qualities. Long service life, absence of corrosion, light weight, ease of installation and affordable cost contribute to the expansion of the use of PE products, making them a worthy alternative to metal pipes.
Polyethylene pipes: what are they?
Polyethylene pipes are products made of polymers and intended for transporting liquids and gaseous substances, sewage installations and as insulating material for electrical and telecommunications. Polyethylene pipes are marked with the abbreviation PE (in international practice - PE). Depending on the production technology and purpose, these types of polyethylene pipes are distinguished.
- HDPE is a product made from low-pressure polyethylene (or high-density polyethylene), produced by extrusion of ethylene at reduced pressure and high temperatures using catalysts. The result is a high-strength material, which expands the possibilities of using pipes made from it. The types PE 80 and PE 100 are widely used, the latter brand being more popular. Such pipes are used for pressure and non-pressure systems for water supply, sewerage, and transportation of other liquids and gas. You can read about the features and use of PE 100 polyethylene pipes in more detail in another article - “PE-100 polyethylene (HDPE) pipes.”
- LDPE - pipes made of high pressure polyethylene. Produced by polymerization under high pressure. The result is a material that is lightweight, but more flexible and soft than low-pressure PE. The scope of application of this type of pipe is mainly the organization of water supply and sewerage systems.
- PE-X - pipes made of the so-called “cross-linked” type of polyethylene. This type of pipe is made from high-density PE by bonding its molecules with butene molecules. The result is a high-strength, high-temperature-resistant material with additional bonds - hence the name “cross-linked”. Such pipes can be single-layer or multi-layer. There are 4 types of adhesion and, accordingly, the names of such products: peroxide (PE-Ha), silane (PE-Xb), electron flow (PE-Xc) and through nitrogen compounds (PE-Xd). Such pipes are used for the manufacture of hot water supply systems.
- PE-RT - products made of polyethylene with increased heat resistance, a new product in the production of polyethylene pipes. Heat-resistant material is preferably used for installing hot water supply and organizing heating communications, but can also be used for cold water supply. It will be discussed further below.
PE-RT polyethylene was invented to replace PE-X, which creates some problems for the manufacturer: the “cross-linked” type of polyethylene cannot be welded or recycled. Essentially, PE-RT is a thermoplastic that has similar characteristics to PE-X, but does not require a cross-linking process during processing.
Peculiarities
PE-RT polyethylene pipes have a number of unique features that are taken into account when choosing:
- high heat resistance, which provides products with advantages when choosing pipes for hot water supply, organizing heating, including underfloor heating;
- accelerated manufacturing process: to increase hydrostaticity, the product does not require cross-linking;
- high flexibility and ductility ensures ease of installation;
- Product service life is up to 100 years.
In addition to these features, these products have the advantages inherent in all polyethylene pipes - inertness to chemical reagents, lack of corrosion, lightness, ease of installation.
Compound
This type of polyethylene was developed by the manufacturer The Dow Chemical Company. PE-RT polyethylene composition is a copolymer of ethylene with 1-octene. This material was approved by expert commissions and was first introduced into GOST R 52134 (2010) “Thermoplastic pressure pipes and connecting parts for them for water supply and heating systems. Are common technical specifications", and from 01.09. 2015 - in GOST 32415-2013 “Thermoplastic pressure pipes and connecting parts for them for water supply and heating systems. General technical conditions".
Specifications
Polyethylene PE-RT has an increased class of heat resistance and fully meets the standards stipulated by GOST 52134 and foreign quality standards. The technical characteristics of PE-RT polyethylene pipes determine their unique properties as a material for plumbing and heating systems.
- Such systems can withstand pressures from 1.6 to 10 bar, at high temperatures from + 80 °C (emergency level temperatures up to 95-100 °C).
- PE RT pipes are available in various SDRs, the most common being SDR 11, SDR 9 and SDR 7.4.
- External diameter sizes - from 16 to 630 mm.
- The minimum wall thickness is from 2 mm to 62.5 mm.
- Weight of 1 meter - from 0.08 kg to 103.7 kg.
- Thermal conductivity index at 60°C is 0.4 W/mK.
- The elastic modulus, depending on temperature, is from 150 MPa at 90°C to 650 MPa at 20°C.
- The modulus of deformation of shell destruction during bending is at least 10 mm, relative elongation is 600%.
- Bay sizes range from 50 to 600 m.
Production of PE-RT
PE-RT polyethylene has a unique molecular structure with an organization of lateral molecular structures that allows for maximum resistance to hydrostatic stress over a wide range of operating temperatures (from -50 to +80 °C). Through the development of new catalysts, it is possible to control molecular bonds and create new and improved performance characteristics.
The uniqueness of the new PE-RT polyethylene consists in obtaining a material with hydrostatic strength and heat resistance without the need for a cross-linking process. Pipes are produced using a new method: the formation of lateral bonds in polymer molecules occurs without the adhesion process. Raw materials for making pipes come from production in finished form. This technique provides processing advantages over PEX pipe.
Application of PE-RT type II
PE-RT polyethylene pipes come in 2 types. The use of PE-RT type II is preferable to the first, since the new kind polyethylene has advantages: the second type PE-RT can withstand pressure 20% more than the previous generation. Thanks to its excellent technical characteristics, PE-RT type II is used for the following purposes:
- heating installation;
- installation of heated floors;
- cold and hot water supply;
- drinking water pipes.
Mostly PE-RT type 2 pipes, despite the fact that they are a competitor to PE-X in terms of quality and thermal resistance, are used for underfloor heating systems. This is due to the fact that the first generation of Perth pipes could withstand temperatures of no more than 60 degrees.
Heat-resistant polyethylene pipes PE-RT type II have been successfully used on the farm for about 20 years. Thanks to good performance hydrostatic strength even under high temperature conditions, excellent flexibility, this type of product is the best solution for hot water supply communications and heating systems. A wide range of PE-RT pipes are presented on the website in the section “Pipes for hot water supply and heating”.
Advantages and disadvantages of PE-RT type II over other pipes
The question of the disadvantages of PE RT type 2 most often arises during comparison with metal-plastic, PEX and other pipes. Therefore, before we talk about the pros and cons of this pipe, let's take a look at this figure, which shows the long-term strength of polymers based on GOST standards
So, let's look at the pros and cons of PE RT
pros
- flexibility;
- resistant to high pressure and corrosion;
- price-quality ratio;
- a light weight;
- freezing of liquid does not harm pipes;
- liquid passes through them with less vibration and noise;
- ease of installation
Minuses
- poor resistance to ultraviolet radiation (The main disadvantage of PE-RT pipes, like other polyethylene products, is their lack of protection from ultraviolet radiation, so they are not used in communications located within the influence sun rays);
- when the temperature exceeds 80 degrees, the chance of reducing service life increases;
The number of supporters of home heating according to the “” principle is constantly increasing - it has proven its high efficiency and convenience. Indeed, a properly planned, competently installed and well-functioning water floor heating system is distinguished by high efficiency, and therefore cost-effectiveness, the most optimal the microclimate created by it - with rising currents of warm air and a comfortable distribution of air temperature along the height. If we add to this the fact that with such heating the floor surface acts as a heat exchanger, and there are simply no radiators that do not fit well into the interior, then the growing popularity of this type of room heating receives a complete logical explanation.
Accordingly, the number of home owners who are seriously considering a complete transition to water underfloor heating is increasing. However, it should be noted that this is a rather complex and very large-scale undertaking. In addition to the difficulties with conducting construction work, it is necessary to correctly calculate and select heating equipment, distribution fittings, special instruments and monitoring, control and safety devices. And finally, a very important point is the pipes themselves for the warm water floor. Special attention should be paid to these components of such a heating system, due to the fact that the main load - both thermal and mechanical - falls on them.
What should the pipes for a warm water floor be like?
This material has a full “bouquet” of all kinds of positive qualities. Copper pipes conduct and transfer heat well. This material has excellent ductility along with high mechanical strength. Copper is a very durable metal due to its chemical properties. capable of special features Excellent corrosion resistance. Moreover, in modern pipes the copper walls are also covered with an additional high-strength polymer film - service life similar products are calculated over many decades.
Copper pipe - practically no drawbacks, except for a very high price and installation difficulties Lack - Enough complex installation, which requires special tools and stable skills to work with it. This greatly limits the possibility of independently creating such a heating system. But, probably, this is not even the main thing - the cost of such pipelines, especially in comparison with polymer ones, is extremely high, and, alas, is affordable to very few.
Corrugated Steel Pipe
And this is probably the only one types of pipes that It is not prohibited to splice along the length of the heating circuit - their fitting connections are considered so reliable.
Such pipes are made from of stainless steel, they bend easily and retain their given position well. The problems of corrosion resistance, high heat transfer and mechanical strength are not even raised here - such pipes fully meet these requirements. They are given special additional protection by a special coating made of high-quality high-density polyethylene.
Such pipelines, by the way, are actively used on production lines in the chemical industry of many developed countries - and this says a lot. And yet they are not yet widely used in private residential construction. The main reasons are high prices and, perhaps, even a lack of information among home owners about such materials.
The production form of corrugated stainless pipes is ready-made sections of various lengths or coils up to 30 or 50 meters long.
Polyethylene-based pipes
Here it is necessary to immediately make one important note. If you read the variety of articles on water pipes used for heating circuits, you will notice one common mistake. The authors divide the variety of flexible pipes into metal-plastic and made from cross-linked polyethylene. From such a presentation, the reader often gets the misconception that metal-plastic products use some kind of ordinary polyethylene, and in addition to this, there is also cross-linked polyethylene. Nothing like this! All used in modern production technologies types of polyethylene have one degree or another of cross-linking. And it will be better to distinguish between pipes using other criteria - based on polymer processing technology and the structure of the pipe itself.
What is cross-linked polyethylene PEX?
If you don’t figure this out right away, you can simply get confused in the concepts in the future.
Polyethylene, known to everyone and so popular in the production of many household items, for all its advantages, is still not stable. It has a pronounced linear molecular structure, these “chains” are in no way connected to each other, and even with a slight temperature effect, ordinary polyethylene simply begins to “float”. It cannot be used in products that are subject to thermal stress.
It’s a different matter if the mentioned molecular chains are “stitched” - that is, stable numerous cross-links are created, transforming the linear structure into a three-dimensional one. In this case, the polymer does not lose any of its positive characteristics, and plus it gains stability. The more such intermolecular “bridges” there are, the higher the so-called degree of cross-linking (measured as a percentage), and the better and stronger the resulting material.
Moreover, cross-linked polyethylene has a very unique “memory” property. Products made from it, deforming to a certain extent from mechanical, baric or thermal loads, always tend to return to their original shape once given to them after the external influence stops completely or weakens. This is an extremely important feature specifically for pipe production.
Cross-linked polyethylene has the accepted designation PEX. Cross-linking, that is, the creation of transverse intermolecular bonds, is technologically carried out in different ways.
- PEX-a - with this technology, the formation of new bonds is caused by chemical treatment of raw materials with peroxide. Of all existing methods– it is this that gives the maximum degree of cross-linking (about 85%), polyethylene does not lose any elasticity, it turns out to be highly durable and with a pronounced “memory”. The disadvantage of the technology is its rather high complexity and high cost. However, the process is completely controlled, which allows us to obtain material with strictly specified qualities.
- PEX-b - this technology appeared later and was initially considered as a simpler and cheaper alternative to PEX-a. It would seem that this cross-linking technique, which was a win-win and cheap method using water vapor, did not fully justify the hopes placed on it. The material turns out to be not so elastic, that is, there will certainly be restrictions on its bending radius. And at the same time, the degree of crosslinking is only about 65%. During production, it is extremely difficult to control the process, so often such pipes do not fully comply with the declared characteristics. In a number of European countries, PEX-b pipes are not allowed for use in heat distribution networks. There is another interesting feature - the sluggish process of stitching in PEX-b polymer never stops. That is, over time, the material significantly changes its characteristics, becomes stiffer, and shrinks, so PEX-b pipelines often require regular tightening of connections, and metal-plastic pipes can delaminate.
- PEX-s - in this case, the sewing process is caused by directed electron radiation. The production of pipes from such plastic is characterized by low cost, but the material, it must be said, is significantly inferior in quality characteristics to the same PEX. Nevertheless, such a polymer is still used, for example, in the manufacture of inexpensive metal-plastic pipes.
- PEX-d – almost completely removed from industrial applications a technology in which intermolecular bonds were obtained by treating raw materials with special nitrogen compounds.
PEX cross-linked polyethylene pipes
Having undergone special processing, cross-linked polyethylene is very widely used for the production of various types of pipes, some of which are quite suitable for creating, and some are even specifically designed for these purposes.
- For quite some time now, craftsmen have been actively using metal-plastic pipes PEX-Al-PEX for the contours of heated floors. It would seem that such a material is suitable for such purposes like no other. It combines the advantages of both polymer and metal, easily bends into the desired curved shape (subject to certain technologies) and holds the configuration given to it, and conducts heat well.
This is where you need to pay special attention to the specific type of polymer used to produce this pipe. As already mentioned, the optimal solution would be PEX pipes, although they are, of course, much more expensive.
There is another one with metal-plastic pipes important nuance– there are too many counterfeit, obvious and low-quality fakes on the building materials market, absolutely unknown manufacturers who do not accompany their products with any documents or guarantees. Therefore, when purchasing metal plastic, you should never be shy - you must be persistent and demand that the products be presented with certificates of quality and compliance with existing standards.
But even high-quality PEX-Al-PEX pipes still have significant drawbacks. Thus, the heterogeneity of the wall material, and hence the coefficient of linear expansion of the layers, leads to their delamination over time. The only question is time - but this process is inevitable. The inner layer of PEX is forcedly narrowed (to about 0.8 mm), and does not always cope with peak loads (any experienced plumber can tell you about ruptures of metal-plastic pipes). Wherein thin layer foil (from 0.2 to 0.4 mm), even with ideal welding, cannot become a barrier to critical pressure.
For their manufacture, PEX-a or PEX-b are used. The pipe wall can have a completely monolithic structure, or be equipped with a special layer of EVON¸ which serves as an oxygen barrier.
These pipes are very convenient to lay out when installing “warm floor” circuits. They have good ductility, which allows installation with a minimum step between adjacent loops.
All leading manufacturers necessarily equip their products with reliable connecting fittings, which makes installation quite simple and an understandable activity.
When choosing any polymer pipes, you need to understand at least a little about the system of their classification and labeling. It may vary slightly depending on the manufacturer, but still basic principles are saved. You can consider it with a specific example.
1- in the first place, the specific model of the pipe and its brand are usually indicated.
2 – outer diameter of the pipe and total thickness of its walls.
3 – special European standards indicating the possibility of using pipes. In this case, this is an indication that the pipe is suitable even for drinking water.
4 – applied technology for quality control of finished products.
5 – polyethylene cross-linking technology (in accordance with Engel classification, which was described above).
6 – correspondence of pipe parameters in terms of operating temperature and pressure European standards DIN 16892/16893. Specific values of operating parameters and service life can be indicated in the accompanying documentation in the form of a plate:
It also happens that these values are applied directly to the pipe body - for example "DIN 16892 PB 12/60 °C PB 11/70 °C PB 9/90 °C".
7—information about the date and time of production, line or machine number, etc.
In addition, this is usually followed by a pipe length mark - every meter. This simplifies both the implementation of pipes and the work with them directly during installation.
Video: useful information about cross-linked polyethylene pipes
Polyethylene pipes RE- RT
A technological breakthrough can probably be considered the emergence of a completely new type of polyethylene in the production of pipes - PE-RT(short for " Polyethylene oof Raised Temperature resistance"—polyethylene with increased heat resistance). By and large, it is not a crosslinking product, and even the initial raw material, granulate, already has the necessary qualities– numerous and stable intermolecular bonds.
This became possible with the development of technologies for controlled processes of spatial formation of macromolecules. Such polymers open up the broadest opportunities– you can create materials with precisely specified characteristics, focusing on one or another property.
The complex mesh structure of the lattice allows you to dramatically increase the resistance of the material to external and internal loads, to cracking during bending. And at the same time, the material, unlike PEX, remains thermoplastic, that is, it can be connected not only using mechanical adapters (fittings), but also using welding, which significantly increases the reliability of joints if necessary.
Polyethylene PE-RT are being used on an ever wider scale, and there is a strong tendency that over time it will completely displace its “stitched brother” - PEX. All this is thanks to a whole “bouquet” of their positive qualities:
- Pipe production PE-RT- much simpler, the material does not require crosslinking, all intermolecular bonds are already incorporated in the semi-finished product. By the way, this polyethylene can be easily recycled without loss of quality.
- The service life of such pipes is about 50 years or more.
- Pipes PE-RT are not afraid of freezing - they are able to withstand several cycles of complete freezing of water without losing the integrity of the walls.
- Unlike PEX, such pipes are easy to repair.
- The contours of these pipes do not creak in a “warm floor” and are absolutely silent even with high intensity water flow.
Polyethylene is used PE-RT, just like PEX, both for the production of metal-plastic pipes and for purely polymer ones.
In both cases, the performance characteristics are significantly higher than using cross-linked analogues.
When manufacturing a polymer pipe without a metal insert, manufacturers often use their own proprietary developments to ensure oxygen impermeability walls For example, this could be an airtight OXYDEX layer, or a special anti-diffusion EVON barrier.
The main operational characteristics of such pipes are given as an example in the following table:
| Index | 16 × 2 mm | 20 × 2 mm |
|---|---|---|
| Volume (l/linear m) | 0.113 | 0.201 |
| Weight (kg/linear m) | 0,071 | 0.127 |
| Minimum bending radius – 5d (mm) | 60 | 100 |
| Temperature (°C) | 20 | 20 |
| Pressure (bar) | 20 | 20 |
| Service life (years) | more than 50 | more than 50 |
| Temperature (°C) | 75 | 75 |
| Pressure (bar) | 10 | 10 |
| Service life (years) | more than 50 | more than 50 |
| Temperature (°C) | 95 | 95 |
| Pressure (bar) | 6 | 6 |
| Service life (years) | more than 50 | more than 50 |
| Ultimate pressure (bar) | 6 | 4.5 |
| at temperature (°C) | 110 | 110 |
| Ultimate pressure (bar) | 11 | 10 |
| at temperature (°C) | 90 | 90 |
| Linear elongation coefficient max at t=95°С (1/°С) | 1.8 1E-4 | 8.2 1E-5 |
| Thermal conductivity coefficient (W/K m) | 0.41 | |
| Internal surface roughness (µm) | 0.125 (Class 10) | |
| Design strength of material (Mpa) | 6.3 |
To summarize what has been said, it can be noted that polyethylene pipes PE-RT today they are probably the material that best meets the requirements of a “warm floor” system, while remaining in the sector of reasonable affordability.
How much will it cost to buy pipes?
It depends, Firstly, on the length of the heating system circuits. – you can find out by reading the corresponding publication on our portal.
When making calculations, one should not forget about the sections from the floor to the distribution manifold, taking into account the connecting margin of at least 500 mm at each end.
The cost of pipes may depend on the manufacturer, the specific model, and the region where the material is purchased. The products of well-known European companies – “Uponor”, “Rehau”, “Kermi”, “Henco”, “Oventrop” and others - enjoy the greatest authority and, accordingly, demand. For example, the table shows several models of pipes suitable for “warm floors”. Prices are indicative, typical for the central regions of Russia:
| Manufacturer, brand | Diameter, mm | Brief technical specifications | Coil length | Price per 1 linear meter |
|---|---|---|---|---|
| Uponor PEXа evalPEX Q&E 16 x 2.0 | 16 | Cross-linked polyethylene, wall 2 mm, t max – up to 95 degrees, (short-term heating up to 110) | 50 – 240 m | 90 rub |
| Uponor PEXа evalPEX Q&E 20 x 2.0, | 20 | -//- | 50 – 120 m | 114 |
| REHAU "Rautitan stabil" | 16 | Metal plastic, PE-Xc/AI/PE wall 2.6 mm | 100 | 105 |
| REHAU "Rautitan stabil" | 20 | Metal plastic, PE-Xа–AL–PE wall 2.9 mm | 100 | 150 |
| REHAU "Rautitan flex" | 16 | Cross-linked polyethylene RAU-PE-Xa, wall 2.2 mm | 100 | 105 |
| Kermi MKV xnet 16 x 2.0 | 16 | Metal-plastic, PE-Xс–AL–PE–Xс | 100 | 55 |
| REHAU "Rautitan Pink" | 16 | Cross-linked polyethylene RAU-PE-Xa, wall 2.2 mm, t swing - up to 90 degrees | 120 | 64 |
| Wieland cuprotherm CTX | 20 | Copper pipe in a plastic sheath, wall 2 mm | 50 | 240 |
| FLEXSY-20 | 20 | Corrugated annealed stainless steel pipe with polymer coating, wall 2 mm | up to 50 | 175 |
| BioPipe PERT 16x2.0 | 16 | Monolayer, t max – up to 100 degrees, pressure – up to 6 bar. | 240 m | 35 |
| Thermotech MultiPipe PE-RT II, 16*2 mm | 16 | Five-layer with diffuse barrier | 240 m | 85 |
The table deliberately does not indicate the most inexpensive types of pipes, from unknown or very dubious manufacturers. You should think carefully before buying cheap, unreliable products, since the water-heated floor system, poured concrete screed, should not cause the home owner any cause for concern.
And finally, a video assessing pipes for a “warm floor” system from a specialist.
Prices for water pipes
Water pipes
Video: which pipes are better for “warm floors”?
Many private houses are heated using water heated floor systems. This factor is explained by the efficiency of this type of heating. The coolant circulating through the pipeline laid under the floor has a much lower temperature than in radiators. This means that much less energy resources are spent on heating it.
Warm floors do not spoil the interior of the premises at all, since they are hidden from the eyes of others finishing coat. And the air, heated over the entire surface of the floor, is always directed upward, creating a favorable microclimate and increasing the level of comfort.
Ideally, the use of such heating systems should be envisaged at the stage of building a house. Otherwise, you will need to carry out calculations and large-scale work that requires certain skills and craftsmanship. In addition to choosing high-quality heating and pumping equipment, it is necessary to pay close attention to the selection of consumables, the main of which is the pipe.
It is a mistake to believe that any pipe can be laid in a concrete screed. Increased demands are placed on this element of the system, since the service life of the heated water floor and the quality of operation of the entire system will depend on it.
And although this consumable material is presented in a huge assortment on the construction market, not each of them meets all quality and safety requirements.
Which pipe is suitable for laying the water circuit and will not only extend its service life, but also save money? What do the designations PEX and PE-RT mean? What are the advantages of PERT polyethylene, which recently appeared on the Russian market?
Requirements for pipes
In most cases, the contours of a water-heated floor are filled with a heavy concrete screed, closed with a finishing finish. Even after removing tiles or removing part of the laminate, carry out visual inspection system for leaks or any other malfunctions will be impossible.
Therefore, any pipe that is part of a water-heated floor system must meet the strict requirements stipulated by special conditions its operation.
The main element of water heated floor systems has a standard diameter, which can correspond to the following values:
It should be noted that when using consumables of a smaller diameter, heat transfer decreases, which leads to a reduction in the distance between the loops of the circuit and, accordingly, to an increase in material consumption. In addition, the small diameter of the pipe leads to overloads of the pumping equipment. It is inappropriate to use and pipes are too large diameter, since in this case the thickness of the concrete screed will increase and, as a result, the load on the floor.
DIY water heated floor
What materials are pipes for heated floors made from?
So what material should be preferred when installing water-based floor heating systems? And here you should not rely on sellers’ assurances that all their goods comply necessary requirements. Such carelessness can lead to problems that arise already at the installation stage of the systems.
Several materials are used in the production of pipes for heated floors.
- Polypropylene. This option is the most budget-friendly. And this is perhaps his only positive quality. It will not be possible to mount a circuit from a single piece of pipe, since they are sold in small meters. This material is not highly plastic, so laying the contour is possible only if big step between the loops. And most importantly, polypropylene has a very low heat transfer coefficient, so the system will be ineffective.
- Metal. Metal pipes can be made of copper and corrugated steel. These materials are different high quality and durability. But their significant disadvantage is their high cost, which is unaffordable for most of the population.
- Polyethylene (PEX and PE-RT). This also includes metal-plastic. In the production of all varieties we use different kinds polyethylene, and each pipe has a special structure and is processed using various technologies. These materials are distinguished by ease of installation, resistance to mechanical and temperature influences, as well as affordable cost.
PEX pipes
First of all, you need to understand what the term “cross-linked polyethylene” or PEX means. Many household items are made from polyethylene. However, in its original form, this material is sensitive to high temperatures.
And it’s all because of the structure of the material, the molecules of which are not connected to each other in any way. This drawback is eliminated by using a special treatment of polyethylene, which allows the molecules to be “cross-linked”, due to which the polyethylene becomes stable and does not melt under the influence of high temperatures.
Pipes for heated floors
As a result of such processing, the PEX pipe acquires another positive quality, which is the ability to return to its original shape. That is, if during the operation of water heated floor systems the pipe experiences overload or is subject to mechanical stress that changes its position, after reducing the intensity of the load it will take on its originally specified shape.
Cross-linking of polyethylene is done using different technologies, denoted as follows:
It should be noted that when arranging water circuits, PEX-a pipe is most often used. The next two varieties are used much less frequently due to their lower quality. And PEX-d pipes in last years and are not used at all.
PE-RT polyethylene pipes
The designation on the pipe “PE-RT” means that it is made of polyethylene with increased heat resistance. This concept does not mean that cross-linking technology was used in relation to it, since the unique PE-RT material already has all the necessary qualities. Distinctive feature PERT pipes is the possibility of connection in the circuit using welding or fittings. Regardless of the type of work performed, PERT does not lose its strength and ductility.
PERT polyethylene is also used in the production of metal-plastic pipes, distinctive feature which is the presence of an internal aluminum layer. If a PE-RT polyethylene pipe is produced without an internal metal layer, it is protected from oxygen penetration by other means, for example, by an airtight layer of OXYDEX.
A water heated floor mounted from a PERT pipe has higher performance characteristics. This material, unlike PEX, has increased elasticity and the ability to withstand heat up to 124.7°C. Considering the lower cost of production of PE-RT polyethylene, the installation of heated floor systems from PE-RT pipes is somewhat cheaper, while meeting all the requirements for this method heating
Video: Warm water floor
Do you dream of comfort? Do you want a warm floor in winter, and in summer - cold ceiling and walls? All this can be achieved with modern polyethylene pipes: cross-linked PEX and heat-resistant PERT. They can be installed without the help of specialists with your own hands. Read the article about how to select and install polyethylene pipes.
1. What types of pipes are there?
There are 5 main types of pipes:
Steel or galvanized (ferrous metal - an alloy of iron with carbon and other elements)
Copper (non-ferrous metal)
Metal-plastic
Polypropylene
Polyethylene (made of cross-linked polyethylene)
Each of the above types has its own purpose and is suitable for certain methods of laying pipelines and the properties of the transported medium (maximum and minimum temperature and pressure).
Today, heavy, unaesthetic metal pipes are being replaced by lightweight metal-plastic, polypropylene and polyethylene pipes. They are different colors and do not require painting, they can be laid in any way - open, hidden or combined.
2. Purpose of cross-linked polyethylene pipes
XLPE pipes
Polyethylene pipes (PE) are used for:
- cold and hot water supply;
- low-temperature water heating (usually up to 80°-95C);
- water heated floors and walls;
- “cold panel” systems (an alternative to air conditioners that eliminates drafts and excess dust);
- cooling artificial ice skating rinks;
- soil heating in greenhouses;
- process pipelines for food and non-food liquids and gases, etc.
3. Advantages and disadvantages
Advantages:
low cost; a light weight; ease of installation; resistance to liquid freezing (if water freezes, the pipes will only stretch a little, and after thawing they will return to their previous size); absorption of noise and vibration during liquid transportation; reliability and long service life (up to 50 years or more) when used in low-temperature systems.Flaws:
low oxygen permeability of single-layer polyethylene pipes, which over a long period of time can lead to corrosion of system elements; reduced service life when used in high-temperature heating systems; instability to ultraviolet (solar) radiation when exposed for a long time.4. What are polyethylene pipes
Depending on the production technology, there are 3 main types of PE pipes:
- HDPE (low-density polyethylene, another common name is high-density polyethylene);
- MSD (medium pressure and density polyethylene);
- LDPE (high pressure and low density polyethylene).
The following materials stand out:
- PEX (cross-linked polyethylene);
- PERT (heat resistant polyethylene).
HDPE, PSD and LDPE pipes are manufactured under different pressures, which influence the process of ethylene polymerization (combination of small gas molecules into larger macromolecules).
PEX and PERT are made from HDPE and PSD using the “cross-linking” and “adhesion” technology.
Cross-linked polyethylene is produced from high-density polyethylene by chemically or physically cross-linking its molecules with molecules of “flat” butene.
During the production of heat-resistant PERT, polyethylene molecules adhere together medium density with “bulk” octene.
Despite these differences, PEX and PERT materials have similar properties. Therefore, it is no coincidence that manufacturers lump them into one category (for example, you may see PEX and PERT pipes in the same section on plumbing company websites).
PEX and PERT pipes are:
- single-layer;
- multilayer.
In cross-section, multilayer pipes represent a three-layer or five-layer structure.
In a three-layer pipe, a layer of polyethylene is covered with glue, on top of which an anti-diffusion layer is applied, which prevents the penetration of oxygen and other gases into the water and thereby has an “anti-corrosion effect.” Polyvinylethylene EVOH or ethylene vinyl alcohol EVAL acts as an “oxygen barrier” that extends the service life of the system.
In a five-layer pipe, the anti-diffusion layer in the center is covered with layers of glue, on top of which layers of polyethylene are applied.
5. How to choose the pipe diameter
When choosing new pipes, pay attention to the size of the old ones. To replace it, you need to select a product of the same or slightly larger diameter.
For example, on your still functioning metal pipes it says “DN 15”: the number in this case means the internal diameter. And on modern polyethylene pipes, manufacturers indicate the outer diameter and wall thickness.
To calculate the internal diameter, you need to subtract the wall thickness multiplied by two from the size of the external diameter. For example, the plastic says 20x2.0. 20 – 4 (2.0x2) = 16 mm. This means that a 20x2.0 polyethylene pipe with an internal diameter of 16 mm is suitable for replacing a DN 15 steel pipe.
Table 1. Calculation of the internal diameter of plastic pipes of the most common sizes
6. Which pipes are best to buy?
To choose quality products, pay attention to the type of material (indicated on the pipes themselves, the label or in the product description on the website).
There are two types of PERT material – Type I and II. Type 2 PERT can withstand 20% higher pressure than the previous generation, i.e. Type I.
When comparing PEX and PERT, PEX is considered more durable because it can withstand high temperatures and pressure longer.
Usually the letters a, b or c are added to the PEX inscription, which indicates the method of cross-linking polyethylene and affects their quality. PEXa and PEXb are produced chemically, PEXc - physically, and the degree of crosslinking of PEXa reaches 75%, PEXb - 65%, PEXc - 60%. Tests of the last three types of polyethylene pipes of the same size at a temperature of 90°C showed the advantage of PEXb.
In addition, the quality of the pipe depends on the thickness of its wall and the method of applying oxygen-impermeable layers.
Tests have shown that a three-layer pipe is more reliable than a five-layer pipe. In a three-layer pipe, the polyethylene layer is monolithic over the entire cross-section of the pipe; in a five-layer pipe, it is interrupted by an anti-diffusion layer and glue, due to which the intermolecular bonds of polyethylene are interrupted. If it overheats construction hairdryer delamination is possible during bending. The hardness of the EVOH layer is significantly higher than that of PEX, so if properly transported, damage and abrasion of the outer layer is unlikely.
Table 2. Comparative characteristics of PEX pipes from various manufacturers
| Manufacturer | Valtec | Pro Aqua | Rehau | Birpex | Royal Thermo | Uponor | TEBO technics | Sanha |
| Polyethylene material | PEXb, PERT type II | PERT type II, PEXa | PEXa | PEXb, PERT | PEXb, PERT type II | PEXa | PERT type II | PEXc |
| Number of layers, pcs | 1-3 | 1-5 | 1-3 | no data | 5 | 1-3 | 1-5 | 5 |
| Outer diameter, mm | 16-20 | 16-40 | 10,1-63 | 16-63 | 16-20 | 16-110 | 16-26 | 16-20 |
| Wall thickness, mm | 2 | 2,2-5,5 | 1,1-8,6 | 1,8-8,6 | 2,2 | 2-15,1 | 2-3 | 2 |
| Working pressure, bar | 6-10 | 6-10 | 8-10 | 6-10 | 10 | 6-10 | 10 | 6 |
| Maximum operating temperature, °C | 80-90 | 90 | 70-95 | 80-95 | 95 | 95 | 95 | 95 |
| Manufacturer country | Italy-Russia | Germany | Germany | Russia | Russia-Italy | Finland | Türkiye | Germany |
| Service life, years | 50 | 50 | 50 | 50 | 50 | 50 | 50 | 50 |
| Manufacturer's warranty, years | 10 | 10 | 1 | 5 | 8-10 | 10 | 7 | 1 |
| Delivery method | bays | bays | bays | bays | bays | bays | bays mi | bays |
| Price per 1 linear meter, rub. | from 33 | from 26 | from 96 | from 43 | From63 | from 52 | from 68 | from 28 |
*Prices according to online sources are valid for February 2018.
To assess the applicability of pipelines to a specific system, pay attention to the declared operating classes of products according to GOST (and certificates of compliance with them). They will show the share of the influence of those changing in summer and winter periods temperatures for the actual service life. Example:
Table 3. Reliability requirements for polyethylene pipes according to GOST R 52134-2003
| Operating class | T slave, °C | Time at T pa b, year | T max, °C | Time at T max, year | T avar,°C | Time at T emergency, h | Application area |
| 1 | 60 | 49 | 80 | 1 | 95 | 100 | Hot water supply (60 °C) |
| 2 | 70 | 49 | 80 | 1 | 95 | 100 | Hot water supply (70 °C) |
| 3 | 30 | 20 | Low temperature underfloor heating |
||||
| 40 | 25 | 50 | 4,5 | 65 | 100 | ||
| 4 | 20 | 2,5 | High temperature underfloor heating Low temperature heating with heating devices |
||||
| 40 | 20 | 70 | 2,5 | 100 | 100 | ||
| 60 | 25 | ||||||
| 5 | 20 | 14 | High temperature heating with heating devices | ||||
| 60 | 25 | 90 | 1 | 100 | 100 | ||
| 80 | 10 | ||||||
| HV | 20 | 50 | - | - | - | - | Cold water supply |
The following notations are used in the table:
T slave - operating temperature or combination of temperatures of transported water, determined by the area of application;
T max - maximum operating temperature, the effect of which is limited in time;
T avar is an emergency temperature that occurs in emergency situations when control systems are violated.7. Installation methods
There are three main ways to install wiring:
- Hidden;
- Open;
- Combined.
7.1. Hidden
With hidden installation, the pipeline and all connections are “hidden” in special recesses - grooves. Only fittings (connectors) and bends for connecting plumbing fixtures are visible from the outside. Upon completion of the work, the surface is sealed with finishing materials.
This method protects pipes from accidental damage and preserves the aesthetic appearance of the interior. However, this same installation option complicates the process (due to gating - laying channels), increases the cost of work and is not suitable for load-bearing walls.
TO hidden installation This also includes covering pipes with concrete screed in “warm floor” systems.
7.2. Open
If the pipes cannot be hidden in the wall (for example, after a recent renovation), they can be laid on the surface. This option is convenient for visual inspection of connections and allows you to quickly clean the area or replace a component if necessary. Additional arguments in favor of the method are the ease and low cost of work.
7.3. Combined
The combined method involves laying unfinished walls on the surface, which are then covered with plasterboard boxes or false panels made of plastic, tiles or other materials.
For installation, one of two connection systems is usually used:
- sequential
- collector
At sequential system the pipe is laid from one object to another. This system is suitable for bathrooms with a minimum number of objects (bathtub, sink, washing machine).
IN collector system all control devices are located in a compact manifold, which is placed in a special cabinet. Using a collector simplifies the work process and saves money. Suitable for radiator wiring and underfloor heating.
Tips for installing polyethylene pipes
Installation tips:
Before starting work, consider how the pipes will be placed. Then, directly on the walls, floor or ceiling, use a pencil or marker to draw the lines of the future pipeline. Use the pipe connection to the faucet, radiator or manifold as a starting point.
If necessary, before concealed installation, insulate the fittings with film or the entire pipes with a special corrugated casing. Do not use sharp objects to unpack the coil, as they may damage the material.
Try to minimize the number of fittings that affect pressure stability. For convenience, during the installation of “warm floors” you can use special slabs or mats that facilitate installation and minimize heat loss.
If you decide not to use thermal insulation mats, use anchor brackets and 90°C rotation clamps, as the “molecular memory” of polyethylene pipes will prevent it from maintaining the specified shape.
The same memory effect will help restore the original shape of the PEX pipe in case of excessive bending and deformation: it is enough to heat it with a hair dryer to 100–120 ° C (the temperature depends on the material, it is indicated in the product data sheet).
8. What materials and tools are needed
1. Materials:
- fittings (crimp, press-on, plastic) - special connectors for branching pipes, turns, transitions to another diameter (read more about fittings below),
- fasteners - clamps, brackets, brackets, rotation locks and other elements that secure polyethylene structures to supporting surfaces (most often on walls).
So, you have decided to lay a polyethylene pipeline yourself. In addition to the pipes themselves, you will need:
2. Tools:
- pipe cutter or scissors (different manufacturers call this tool differently);
- electrical or mechanical expander;
- wrenches for compression fittings, a vice (also called a press or tension tool) - for fittings with a sliding sleeve (or press-on fittings).
9. Types of fittings
You can independently install cross-linked polyethylene pipes with with the help of three main types of fittings:
- crimp (they are also called compression or collet);
- press-fit (or fittings with a sliding sleeve);
- plastic.
The range of all types of fittings includes connectors various forms– straight (couplings), angles, angles, water sockets, tees, crosses, which can be divided into two types:
Since compression fittings require maintenance, they are ideal for open and combined installations. They are not suitable for installation in walls or heated floors.
Components of a compression fitting:
- body (fitting) with ring-shaped notches;
- split ferrule;
- screw.
How to proceed:
- Cut the pipe to the required length. scissors or pipe cutter.
- Place the nut on the section first (with the thread towards the connector), then the crimp ring. The edge of the ring should protrude approximately 1 mm above the cut.
- Insert the fitting into the pipe until it stops, tighten the ring and union nut to the edge of the cut.
The connection of pipes using a sliding sleeve is permanent, so such connectors can be used for any type of pipeline laying, even hidden.
Components for the sliding sleeve:
- frame;
- sleeve.
How to proceed:
- Cut the pipe to the required length using special scissors or a pipe cutter.
- Place the sleeve on a section away from the edge (it should not fall into the expansion area of the pipe).
- Insert the expander into the pipe and increase its diameter according to the instructions.
- Remove the expander and insert the fitting body into the pipe until it stops.
- Pull the sleeve onto the fitting using a vice.
Watch video instructions:
Watch video instructions:
10. What to do if you do not plan to install pipes yourself
In the online store Santekhmontazh.rf you can buy pipes made of cross-linked polyethylene from PEXb and PERT (type 2) of the Russian-Italian brand VALTEC and the German ProAqua. They are adapted to the conditions of domestic heat and water supply systems and have a 10-year manufacturer’s warranty. ProAqua products have undergone comprehensive testing and are certified in accordance with Russian standards. VALTEC sanitary ware received the “Brand of the Year” award in the Russian Federation and is widely in demand in the country (in the Moscow region alone, more than 1,200,000 sq. m of residential space are equipped with it every year).
In addition to polyethylene pipes, you can purchase fittings, fasteners and tools for their installation from us, heat insulating boards, manifold cabinets, blocks, etc.
We will help you select all the necessary plumbing equipment to suit your needs, and we will also quickly and professionally install it, if after reading this article you still do not dare to change or lay the pipeline system yourself. Our installation division specializes in installing engineering systems in private and apartment buildings, in non-residential buildings for various purposes.
Pipe Thermotech Thermosystem®(old name Thermotech >MIDI< Composite) является модернизированным вариантом труб PE-RT, полностью изготовленной из материала Dowlex 2344 (тип 1) и 2388 (тип 2) (PE-RT, торговая марка Dowlex принадлежит концерну DOW Chemical Corp.) с большим числом связей между молекулами, с кислородным барьером (EVOH), спрятанным внутрь трубы между слоями полиэтилена. Т.к. все слои являются полимерами, то в результате последовательного соединения слоев образуется труба, как единое целое, стабильная в условиях колебания температуры и давления, с небольшим линейным удлинением, устойчивая к механическим воздействиям.
Let's decipher the abbreviation PE-RT - PolyEthylene of Raised Temperature resistance - polyethylene of increased heat resistance - the secret lies in the large number of carbon bonds in the molecules. The side chains of the linear Standard Polyethylene (PE) molecule are formed by a combination of butene molecules. Two carbon atoms are used to connect the main chains to each other, so the probability of intertwining is low. The side chains of the linear PE-RT polyethylene molecule increase the number of connecting Carbon atoms to 6, while the degree of intertwining is much higher. If the source material for PEX - Polyethylene, with the same monomer content, is not “cross-linked”, then it will provide much less strength under prolonged exposure to pressure.
Warm floor pipe Thermotech Thermosystem®– has an anti-diffusion layer OXYDEX (EVOH polyethylene), which prevents the penetration of oxygen and an anti-creaking layer, which form a single whole with the pipe.
Anti-diffusion layer OXYDEХ: During the production of pipes, a thin layer of modified polyethylene, 0.1 mm thick, is applied to the surface of the “main” PE-RT pipe. This is followed by the same layer of EVOH (ethyl vinyl hydroxide) plastic. Previously, this anti-diffusion layer was applied to outside pipes. Over time, some manufacturers and Thermotech pipes, incl. They began to apply another protective layer of polyethylene on it.
New polymer pipes from Thermotech - ThermoSystem pipes made of PE-RT type II polyethylene - more flexible and more reliable compared to the old ThermoSystem type pipes (12, 17 and 20 mm) due to the placement of an anti-diffusion layer on the inner surface of the pipe with a layer of protective polyethylene. The oxygen barrier is protected from mechanical damage by the entire thickness of the pipe wall
The EVOH layer acts as a diffusion barrier for oxygen, and the polyethylene layer increases the adhesion between the pipe and the diffusion barrier. The barrier is tightly glued to the pipe, making bends of small radii possible without the formation of folds. Oxygen-tightness of pipes Thermotech complies with the DIN 4726 standard (Deutsches Institut fur Normung), and is less than 0.1 g/m2. for 24 hours at 40 °C. OXYDEX layer in pipes Thermotech reliably protected from mechanical damage by a protective layer of polyethylene. The melting point of the anti-diffusion layer is 180° C. These properties allow the use of such pipes at operating temperatures of the carrier up to 95°, and in short-term modes – up to 110° C, that is, mainly in hot water supply and heating systems, heated floors.
Oxygen penetrating the system does not cause any harm to the pipes themselves, it only reacts with metal parts systems, causing accelerated corrosion of heating boilers, pumps, radiators, shut-off and control valves and other metal equipment. This process is especially accelerated when using pipes in systems with elevated temperatures, i.e. in heating systems (especially radiator systems). Unfortunately, SNiP does not have an acceptable value for oxygen penetration in systems made of plastic pipes. Therefore, in reality, pipes without a diffusion layer are often used, which after 5 years leads to the failure of the steel elements of the system. To prevent this from happening, it is necessary to use only pipes in heating systems that meet the requirements of the German standard DIN 4726. It should be noted that today only a few companies can offer pipes that meet the requirements of this standard.
This pipe can withstand high pressure. The lifespan of PERT pipes is determined by nomograms depending on the temperature and pressure of the working medium (as well as all other polymer pipes). According to Russian certification, PE-RT pipes are classified as type “t” (heavy), i.e. withstanding pressure of 20 kgf/cm2.
The THERMOTECH brand produces 5-layer unreinforced pipes for heating and water supply systems:
- Thermotech Thermosystem PE-RT I diameters 8x1, 12x2 mm, 17x2 mm, 26x3 mm
- Thermotech MultiPipe PE-RT II diameters 16x2, 26x3,
- Thermotech Thermosystem PE-RT II diameter 20x2, 32x3 mm
Advantages of Thermotech pipe
Thermotech = reliable + easy to install + inexpensive!
Extreme flexibility and strength without the use of a crosslinker. The secret lies in the large number of carbon bonds in the molecules. To understand the difference, answer the question: what kind of shoes do you prefer to buy - with edging sewn to the sole (analogous to molecular cross-linking of polyethylene) or with a glued sole (analogous to chemical cross-linking of polyethylene or glued plastics)?
The service life of the pipe is over 50 years. It requires virtually no maintenance during operation, which further facilitates the work of public utilities.
Able to withstand high pressures and temperatures. The service life of PERT pipes is determined by nomograms (see appendix) depending on the temperature and pressure of the working medium. According to Russian certification, PE-RT pipes are classified as type “t” (heavy), i.e. withstand pressure 20 kgf/cm2
Polyethylene pipes are 5–7 times lighter than steel pipes. Pipes are produced seamlessly in standard coils 12 * 2.0 mm (1000 m), 16 * 2.0 mm (750 m), 20 * 2.0 mm (650 m), 25 * 2.3 mm (350 m), 32 *3.0 mm (50 m). This significantly reduces transportation costs and makes the work of installers easier.
The temperature linear expansion of PE-RT pipes is several times less than that of standard PEX pipes. When the temperature changes by 50°C, the linear elongation of PE-RT pipes is only 0.3%, and when the temperature changes by 90°C – 0.7%. When cooled, the pipe completely returns to its original shape.
Joining polyethylene pipes is much cheaper, simpler and takes less time. The pipes are connected using brass compression fittings and takes seconds. The entire installer's tool consists of pruning shears and wrench. Therefore, even a non-specialist can change or install the plumbing himself.
No squeaking in underfloor water heating systems.
Due to the low surface roughness (0.125 microns), the pipes are not subject to overgrowing, therefore require virtually no maintenance during operation and are silent at almost any flow rate.
Frost-resistant and able to withstand several freeze-thaw cycles (for example, water).
It has high maintainability. Multiple joining and undocking of the fitting is allowed, while the pipe at the joint retains its properties.
Can be used for transporting food products, aggressive liquids and gases.
Fully meets the requirements modern industry aesthetics of work and operation of pipelines.
Warranty periods: shelf life 3 years, service life 7 years.
The pipe is resistant to chemicals and mechanical wear.
Foreign certification.
The pipe was tested at SKZ (Suddeutsches Kunststoff Zentrum). According to SKZ tests, the service life of PERT pipe is 490 years with a safety factor of 2.5.
According to the TUV (Technisher Uberwaschungs – veren Bayern) conclusion, a pipe with an OXYDEX layer is not subject to oxygen diffusion (does not allow air to pass through).
The production has an international quality certificate ISO 9002.
Russian certification.
GOSSTROY OF RUSSIA No. 0130837*. Application in heating systems.
HYGIENE CERTIFICATES. According to test results at Polymertest LLC, the service life of the MIDI pipe is more than 100 years, depending on operating conditions.
ROSTSTANDARD. Application in DHW and cold water systems.
Certified for heating systems with operating coolant temperatures up to 95°, at peaks up to 110° C (no worse than any other polymer pipes), pressure up to 20 kgf/cm2 (!).
Pipes Thermotech Thermosystem® are manufactured in Germany by the HPG concern to order from Thermotech (Sweden).
DEVELOPER and MANUFACTURER of PE-RT compound Dowlex 2344 - "The Dow Chemical Company"
Materials and articles from "The Dow Chemical Company" in attachments:
- PE-RT, a new class of polyethylene for hot water pipes
- PE-RT, a new class of polyethylenes for industrial pipes
How do pipes for heated floors behave at subzero temperatures? We do not object to the use of pipes in conditions with low temperatures. Moreover, well-known facilities with PE-RT pipes have been operated without problems for years in arenas with artificial ice in Europe.
PERT pipes maintain high strength even at temperatures down to -40°C.
The DOWLEX 2344E material, compared to other polymers, has higher thermal conductivity at negative temperatures (2-3 times higher), which means more power refrigeration units may be reduced.
Thermotech pipes have a mirror-like internal surface, they have a very low roughness (0.125 microns, class 10), this is less than that of PEX pipes and significantly less than that of any metal-plastic pipes. The thing is that in metal plastic pipes The main load is borne by the aluminum layer and therefore the polymer layers in such pipes are of poorer quality than in plastic pipes. Reducing hydraulic losses in Thermotech pipes will reduce the power of circulation pumps.
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