7 tips for choosing pipes for a warm water floor

7 min

A water-heated floor is a solution to the problem of arranging the most comfortable home. It allows you to efficiently distribute heat in the house, and, unlike an electric analogue, requires low operating costs. It is not surprising that underfloor heating systems are becoming more and more popular and often become an independent source of heat in the house. The quality of such a system and its durability are equally dependent on the materials chosen and the professionalism of the installation. We will deal with the peculiarities of choosing pipes for a warm water floor in more detail, and it is better to entrust their installation to specialists for your own peace of mind. Link provides comprehensive information and examples of the work of a leading company engaged in the installation of a water-heated floor in Moscow and the region. All that remains is to acquire suitable pipes.

# 1. Pipe requirements

The advantages of the water system of warm floors are more than enough. This is economical, and uniform heating, and durability, and the ability to regulate the temperature, and the absence of heating radiators, which often only interfere with organizing the interior of a dream. The easiest way is to organize heating with a water-heated floor in a private house – in a high-rise building the task becomes much more complicated. You will need to reconstruct the existing heating system or install your own electric boiler, so as not to disrupt the heating system of the whole house and not to take heat away from the neighbors.
pipes for water underfloor heating 2

The reliability and durability of a warm floor depends largely on the pipes, which will have to be under the screed for decades, maintaining integrity and tightness. The following requirements are put forward for them:

  • durability and ability to withstand pressure and temperature differences. Hot water pipes are not suitable. Pay attention to the products of well-known and reputable manufacturers, which give a guarantee for pipes for 50 years or more;

  • reliable insulation and tightness, because the heating system must be protected from oxidation;
  • elasticity and resistance to bending. During the installation process, the pipes are bent to achieve uniform heating of the floor, therefore, during their installation and further operation, they should not break and crack, thereby violating the tightness of the system;

  • the optimal pipe diameter is 16 or 18 mm, while the floor height increases slightly, and there is no need for additional equipment to ensure the normal hydraulics of the system;
  • the expansion coefficient should be 0.25 mm / mK, thermal conductivity – 0.43 W / mK.

In underfloor heating systems, predominantly metal-plastic and polyethylene pipes are used, less often – copper, polypropylene and corrugated steel pipes. The norms prohibit the use of cast iron pipes.
pipes for water underfloor heating

# 2. Reinforced plastic pipes for underfloor heating

Reinforced-plastic pipes are almost the most widespread. Durability and excellent performance are due to the multi-layer structure of the material. The inner layer is an extruded cross-linked polyethylene, which is responsible for the performance of the pipe. Next comes a layer of aluminum, which is attached to the polyethylene with a special adhesive. Aluminum foil protects against oxygen penetration into the pipe and restrains linear expansion and contraction. The thickness of this layer is 0.2-0.25 mm, depending on the diameter. Foil is welded end-to-end or overlapped, a sealed layer is obtained. There is another adhesive layer on top of the foil, which bonds it to the outer protective layer of polyethylene.
metal-plastic pipes for a water-heated floor 2

Such a structure allows us to talk about the numerous advantages of metal-plastic pipes:

  • excellent flexibility and ability to hold its shape well after bending;
  • thermal conductivity, which is provided by an aluminum interlayer, and resistance to damage and overgrowth due to the use of polymer;
  • installation of such pipes does not require the use of specific equipment, therefore it will be inexpensive;
  • high durability;
  • the ability to withstand temperatures up to 1100C without changing the basic performance;
  • resistance to corrosion and aggressive environments;
  • light weight;
  • good sound insulation. The sound of the movement of the coolant through the system will be inaudible.

Among the disadvantages are the inadmissibility of pipe twisting and bending about the axis, which must be remembered during installation. It is also important to take into account the property of the aluminum layer to be damaged by repeated bending.
metal-plastic pipes for a water-heated floor

No. 3. XLPE pipes

The main competitor of metal-plastic pipes is cross-linked polyethylene pipes. The main indicator of product quality is the quality of the weld, which can be judged by the density of the stitching. The recommended value is 60-85%, processing can be done in different ways:

  • when crosslinked with peroxide, a density of 75% is achieved, this is the most preferred method. These pipes are labeled as PE-Xa;
  • when crosslinked with silane, a density of 65% is obtained;
  • upon irradiation with an electron flow in a magnetic field, the crosslink density reaches 60%.

In the marking, the abbreviation may indicate the range of crosslinking density: HDPE – pipes with the highest density, MDPE – with medium density, LDPE – low.
polyethylene pipes


  • the ability to withstand the temperature of the coolant up to 1200C;
  • resistance to temperature and pressure drops;
  • low weight, sufficient internal section with a relatively small diameter;
  • strength;
  • sufficient flexibility. The minimum bending radius for such pipes is 5 diameters, and this is quite enough for the installation of an effective underfloor heating system;
  • relative ease of installation;
  • low price.


  • the need to rigidly fix the pipe during laying, otherwise it may bend. For fixing, reinforcement or a special substrate is used; a large amount of fasteners is needed to fix the pipes in the required shape;
  • during installation, it is easy to damage the pipe, therefore it is necessary to work with a certain degree of caution.

Cross-linked polyethylene pipes are produced with a diameter of 10 to 110 mm, the length reaches 200 m.
XLPE pipes for underfloor heating

No. 4. Copper pipes for underfloor heating

In terms of performance, copper is an ideal material for arranging water-heated floors. It is not for nothing that in a number of European countries this material is mainly used today.


  • high strength, not compared with polymer analogs. The strength of copper pipes can even be called excessive in the context of warm floors;
  • durability. The minimum service life is 50 years;
  • excellent heat transfer performance, because it is metal;
  • the minimum bending radius among all pipes, therefore, uniform heating is achieved;
  • the ability to withstand temperatures up to 3000C and pressure in the system up to 400 atm;
  • complete impermeability of pipes to gases, resistance to corrosion, liming and rodents.
    copper pipes for water underfloor heating

The widespread use of copper pipes in domestic open spaces is constrained by some of their disadvantages:

  • high price;
  • the need to use special equipment during installation, with which you need to be able to handle. The connection is carried out only with brass fittings, which also raises the cost of installation.
    copper pipes for water floor heating 2

No. 5. Corrugated stainless pipes

Stainless pipes are used even less often than copper ones, despite significant advantages. Such products have a long service life, have high thermal conductivity, bend well, are durable and do not corrode, but cannot boast of a low cost. The biggest drawback is the limited service life of the rubber bands (only 30 years), which negates the durability of the pipes.
stainless steel pipes for underfloor heating

No. 6. Polypropylene pipes

Polypropylene pipes will cost several times cheaper than copper, steel and even metal-plastic pipes, but they still have not become widespread. For underfloor heating systems, products with PN25 marking are used, which are reinforced with perforated aluminum foil. Outside diameter from 21 to 78 mm, wall thickness 4-13 mm.


  • low price;
  • the ability to withstand the temperature of the coolant up to 950C with optimal 550C in the water floor heating system;
  • high strength, service life not less than 25 years.
    polypropylene pipes for water floor heating


  • small bending radius, which often makes it impossible to equip a heating system with the required efficiency. The minimum bending radius of a polypropylene pipe is 8 diameters, which means that pipes with a diameter of, for example, 23 mm can be positioned at a distance of 368 mm from each other, which may not be enough for uniform heating. If the warm floor will be used as an additional source of heat, then the use of polypropylene pipes is justified;
  • installation conditions for polypropylene pipes. The installation is carried out at temperatures above + 10 … + 150C, which is not always possible.

No. 7. How many pipes are needed?

To more or less accurately calculate the required number of pipes, you can use software or arm yourself with graph paper, on which a floor plan is drawn to scale. The diagram must indicate all large pieces of furniture that will stand motionless – there is no need to lay pipes under them: this is unprofitable and harmful for the furniture itself.

The layout of the pipes is applied to the plan. Laying is usually done in one of the following ways:

  • “Snake”. This is a simpler installation option, but it has a significant drawback – uneven heating of the room, which is well understood from the figure. In the first case, one part of the room will warm up much less, since the coolant enters it already cooled, in the second, the distance between the sections with not yet cooled water is too large, so the floor will warm up unevenly, which will be felt when moving;
    pipe-laying snake

  • The “spiral” is more difficult to set up, requires a more professional approach to calculation and installation, but the heat will be distributed evenly across the floor, since the zones with warm and cold water alternate. In addition, there are fewer turning angles, which affects the speed of movement of the coolant in the pipes;
    pipe laying spiral

  • combined system.

When creating a plan, keep in mind that the pipes are laid at a distance of 15-20 cm from the walls, the step between them should be 20 cm, in extreme cases, no more than 35 cm.If a warm floor is the only source of heat energy, then the step should be minimal, that’s why in houses where the warm floor plays only an auxiliary role, the use of polypropylene pipes with a large bending radius is allowed.

A pipe with a diameter of 16 mm is capable of heating 10-15 cm of the surface in both directions. At external walls, it is advisable to take a smaller step in order to provide a reliable barrier to cold. The approximate number of pipes can be calculated using the created scheme, but it is better to take the material with a margin or ask to calculate the specialists who will carry out the installation.

The recommended length of one coolant circuit is no more than 60 m, otherwise the water will cool too much, and you cannot build an effective heating system. If this is not enough to heat one room, then it is better to equip several heating circuits. The data is given so that you can calculate the approximate amount of necessary materials and the costs for them – it is better to entrust the design of the underfloor heating system, as well as their installation, to professionals.

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Passionate about DIY for over 10 years and all the new tools, I give you through this blog all my advice, tips, tests in all areas: carpentry, electricity, masonry, gardening, home automation ...


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