When buying pipes for a heating system, you should first of all focus on their durability, the ability to withstand water hammer and temperature extremes. Ease of installation is also important. So which pipes are better to choose for heating a private house? Let’s talk about this in detail.
Requirements for heating pipelines
According to the norms of SNiP, the equipment used for the installation of heat supply systems must meet certain requirements:
- withstand a working pressure of 0.7-1.5 atm during the entire period of operation;
- maintain integrity during short-term water hammer at a pressure 1.5 times higher than the nominal (working);
- remain sealed at a coolant temperature of 90°C;
- have sufficient chemical resistance and UV resistance;
- be easy to install and maintain;
- have a service life of 25 years; and for pipelines laid in hidden structures (walls, concrete floors) — at least 40 years;
- the material used for their manufacture must not contain impurities harmful to human health;
- to protect against rapid clogging of the system, the inner surface of the pipelines must have an ideal smooth surface, for example, for steel products, the equivalent roughness can be 0.2 mm;
- the diameter of the pipeline must be sufficient to provide heat to each of the heated rooms.
Additional requirements are imposed on the pipelines used for the installation of underfloor heating systems. Such products should be sufficiently flexible and elastic, easily fit into loops without the formation of creases, and keep a given shape well.
Advice! For heating systems, pipes and fittings should be purchased from the same manufacturer. The properties of the materials used for their manufacture, in this case, will be identical. This will ensure better sealing of the joints.
Which is better, steel pipes for heating a private house or plastic? The advantages of metal products include high thermal conductivity and the ability to easily give off heat to the environment. Another indisputable advantage of metal pipes is increased strength, reliability, the ability to withstand even significant water hammer, mechanical stress and temperature changes.
When heated, the thermal expansion of the metal is negligible, so the likelihood of leakage at the junction of the pipes is minimal. In the event of their freezing, processing with a blowtorch or other source of open flame is allowed.
But there are many disadvantages of steel products. The first is susceptibility to corrosion. Even galvanized pipes will last no more than 25 years. In the first years of operation, there are no complaints about them. However, in the process of metal oxidation and the appearance of rust growths, the pipes begin to become clogged. As a result, their throughput is sharply reduced. A similar problem is a real scourge of steel products.
They are also quite complicated in installation — it is possible to bend metal only on special equipment when heated. Another disadvantage is high thermal conductivity. For this reason, it is not recommended to install metal pipes when installing an electric boiler.
Steel pipes stand slightly higher than similar plastic products. However, when choosing them, the cost and installation work should be taken into account. After all, metal welding requires considerable skills and expensive equipment.
An ideal option for installing heating and heating systems would be stainless steel pipes that can last almost forever. However, their use is limited due to the high price and complexity of installation.
HDPE pipes and cross-linked polypropylene
The term HDPE is used for products made from low density polyethylene. Since this type of plastic does not tolerate the effects of elevated temperatures (it is allowed to operate only at + 40 ° C), cross-linked polyethylene (abbreviation PEX) is used for laying heating pipelines. To reduce the thermoplasticity of the material and give strength, its molecules are additionally connected into a three-dimensional network using cross-links. As a result, it easily tolerates elevated temperatures and is able to melt only when it exceeds 200 ° C.
In addition to high temperature resistance, products made of cross-linked polyethylene have the following advantages:
- lack of corrosion, characteristic of any type of plastic;
- increased strength and wear resistance: some manufacturers provide a guarantee for this material up to 50 years under operating conditions at 6 atm nominal pressure and temperatures up to 70-90 ° C;
- the ability to withstand temperatures up to -50°C without loss of tightness; that is, such plastic pipes are not even afraid of freezing;
- increased resistance to chemical compounds — such a material is not able to come into contact with them;
- elasticity: PEX pipes are quite flexible and ideal for installing underfloor heating, they can easily fit into loops without creases;
- environmental friendliness: polyethylene does not emit harmful substances when heated;
- low price:
- ease of installation: for welding polyethylene, the simplest equipment is used, the cost of which is minimal.
Please note that the crosslink density of molecules in polyethylene can be different. Products labeled PEX-a are considered the most expensive. However, they have maximum flexibility and are more suitable for underfloor heating. The crosslinking area of PEX-b molecules is smaller, and the price is not so high. At the same time, they are quite reliable and perfectly respond to pressure drops. But it’s hard to bend them. PEX-c plastic is of lower quality. It is quite flexible, but is able to form creases.
Of course, the best pipes for heating systems are copper. Their main disadvantage is their considerable cost. Otherwise, there are practically no complaints about this type of product. They possess:
- long service life: since such a material is not afraid of corrosion, the service life of products made from it can be 100 years or more;
- increased thermal conductivity;
- high tightness of connections;
- the ability to withstand strong pressure drops, water hammer and temperature drops to -200 ° C, while its melting point is + 1080 ° C;
- almost complete absence of blockages;
- aesthetic appearance.
Connect copper products by capillary soldering, by means of compression fittings or threaded connection with rolling. Copper is also used to create the contours of underfloor heating. However, in this case, a special type of material is used — annealed copper. It is heated to a certain temperature and then quickly cooled. As a result, the pipes acquire greater elasticity and flexibility. Such processing can slightly reduce the strength of the material, but it is quite enough to create an autonomous heating system for underfloor heating.
Since copper is an excellent conductor of current, when installing pipelines from it, mandatory grounding and the installation of dielectric gaskets are required. Dangerous for this material are also eddy currents that can destroy the tightness of the system. Plus, rather soft copper can be easily damaged, so when installing it in a boiler room, you will need to purchase protective covers.
Advice! The combination of copper and steel in the same pipeline is highly undesirable. Steel will begin to rust. If such a connection cannot be avoided, it is worth mounting steel pipes in front of copper pipes (in the direction of movement of the working fluid). Brass reacts less to contact with copper, therefore, in the absence of copper adapters, it is better to use not steel, but brass fittings.
Eco-friendly products made from this type of plastic are used both for laying drinking pipelines and pipelines for heating systems in private houses and apartments. We list the main advantages of this material:
- polypropylene has a fairly long service life (some manufacturers provide a guarantee of up to 50 years), so it can be laid in walls or immured in concrete floors;
- high chemical resistance: this material is not afraid of corrosion, so scale does not form in smooth pipelines;
- sufficient mechanical strength;
- the minimum noise level when passing through the pipes of the working fluid (all metal products, unfortunately, are deprived of this advantage);
- strong monolithic connections by welding or fittings;
- for its welding, inexpensive “soldering irons” are used, the work of which can be mastered in a short time.
Polypropylene costs more than ordinary polyethylene, but less than metal-plastic. Another disadvantage is the low temperature of the coolant — depending on the type of material, it can only be used at a temperature of + 65-95 ° C.
Pay attention to the labeling. If you do not know which of the pipes is better to choose, it is better to stop at PP-R and PP-RCT copolymers, which have not only heat resistance (they can be operated at temperatures up to + 95 ° C), but frost resistance. They are absolutely not afraid of low temperatures. Plastic, marked with the letters PP-C, crystallizes when frozen and becomes too brittle. P-N material does not tolerate elevated temperatures, so it is not suitable for the installation of heating systems. Products marked PP-B are used for systems where the coolant is heated only up to 50 ° C. PPRC material with a reinforcing layer is more resistant to elevated temperatures.
If you do not know which pipes are best used for heating, purchase metal-plastic. It is considered the best material for these purposes in terms of price-quality ratio. To give it rigidity, plastic is reinforced with reinforcement — a layer of aluminum, steel or fiberglass. The inner protective layer is made of smooth materials, PVC, polypropylene or cross-linked PEX, so lime and rust are not deposited on it.
The layer of reinforcement in such pipes creates a strong barrier to the penetration of oxygen. Due to this, metal elements (connecting fittings, pumping equipment, etc.) are less susceptible to corrosion. Plus, inserts made of aluminum or steel significantly reduce the likelihood of thermal expansion and contraction of plastic during heating or cooling. The most stable are products made of reinforced polypropylene or cross-linked polyethylene.
The absence of corrosion and increased physical and chemical resistance allows the material to be used for at least 50 years. Metal-plastic is sold in coils 50-500 m long. Therefore, its laying can be carried out with a minimum of connections, fittings and rotation angle clamps.
Just like propylene pipes, metal-plastics are connected by welding or by means of detachable or conditionally detachable (compression) joints. It bends easily, so products from it do not require special fitting. Such pipes can be connected to products from other materials using fittings.
Reducing the service life is possible only with large pressure surges in the system and long-term use when the temperature of the working fluid exceeds 100 ° C. When operating in normal mode, it can last up to 50 years.
The vulnerable point of this type of product is the adhesive joint, which is used to bind the layers of plastic and reinforcement. When the manufacturer uses low-quality compounds, pipe delamination and leakage are possible.