How to choose the right installation materials for heating: a complete guide
How to choose the right installation materials for heating: a complete guide
The choice of installation materials for heating is a decision that will affect the reliability and lifespan of the entire heating system for decades to come. This is an area where surprisingly many mistakes are made in practice—not because people are careless, but because there is an enormous variety of materials available, and their differences are not always immediately obvious. I have seen installations where someone saved a few euros on fittings, and after three years they had to redo the entire floor heating due to a leak. I have also seen projects where expensive materials were unnecessarily used in places where a cheaper solution would have been sufficient. This guide will help you navigate the full range of options and choose exactly what suits your specific project.
What all belongs to heating installation materials
When we talk about installation materials, most people imagine pipes. That is indeed the foundation, but the actual breadth of this category is much greater. Under the term heating installation, we understand everything that forms the framework of the heat distribution network from the source to each radiator body or floor circuit:
- Pipes and tubes – copper, steel, plastic (PEX, PE-RT, PP-R, multi-layer)
- Fittings and connectors – elbows, T-pieces, reducers, adapters
- Valves and accessories – ball valves, drain valves, air vents, safety valves
- Thermal insulation for pipes – foam rubber, mineral wool, pipe sleeves
- Mounting hardware – clamps, brackets, hangers, expansion joints
- Sealing materials – Teflon, hemp fiber, liquid sealants, O-rings
- Distributors and collectors – manifolds for floor heating or multiple circuits
- Pumps and control elements – circulation pumps, thermostatic heads, mixing valves
- Expansion vessels and pressure gauges
Each of these components plays an irreplaceable role. Omitting or underestimating any group often leads to problems—either functional or operational. Let's take a closer look at each group.
Pipes: the most important decision in the entire installation
Choosing the pipe material is a fundamental step, from which everything else depends—fittings, connectors, tools, installation techniques, and long-term reliability. Currently, four main material groups are used in apartments and single-family homes:
Copper tubes
Copper is a classic with proven decades of use. Copper tubes are highly durable, have excellent thermal properties, and their lifespan is around 50 years or more. They are joined by soldering (hard or soft soldered joints), pressing (press fittings), or screwing (compression fittings). The disadvantages are the higher material cost and the need for special tools and skills when soldering. In practice, copper is still widely used in boiler rooms, on primary circuits, and wherever high temperature resistance (up to 110 °C) and pressure strength are required.
Typical dimensions for apartment distribution: DN 12, DN 15, DN 18, DN 22 – for risers and main distribution DN 28 or DN 35 is used. More about dimensions can be read in the article Pipe diameters and dimensions for heating: what you need to know before purchasing.
Plastic pipes – PEX, PE-RT and PP-R
Plastic pipes have gained a dominant position in floor heating and are increasingly used in radiator distribution over the last two decades. Their main advantages are lower cost, easy installation (easy cutting, bending), corrosion resistance, and quiet operation without flow noise.
PEX (cross-linked polyethylene) – cross-linked polyethylene exists in three types: PEX-a (Engel method), PEX-b (silane cross-linking), and PEX-c (electron cross-linking). For heating, the key property of "shape memory" in PEX-a is important, which allows the pipe to return to its original shape when heated—used in expansion joints. Operating temperature: up to 95 °C, pressure up to 6 bar at 80 °C. Important: PEX pipes must have an oxygen barrier (EVOH layer) when used in heating—otherwise oxygen diffuses into the water and causes corrosion of metal components (pumps, boiler, radiators).
PE-RT (polyethylene of raised temperature resistance) – polyethylene with increased temperature resistance, suitable for floor heating and low-temperature systems. Compared to PEX, it has the advantage of weldability and lower cost, but it does not have shape memory. It also requires an oxygen barrier.
PP-R (polypropylene random copolymer) – joined by polyfusion (thermal welding) and forms permanent, absolutely sealed joints. An advantage is zero oxygen diffusion (no barrier), resistance up to 95 °C and long service life. A disadvantage is a higher coefficient of thermal expansion (need for compensators) and less flexibility when bending.
Multilayer pipes
Multilayer pipes combine plastic and aluminum in several layers (typically: inner plastic layer – aluminum sheath – outer plastic layer). Aluminum prevents oxygen diffusion, minimizes thermal expansion and at the same time retains flexibility and easy installation. They are joined by pressing or threaded fittings. In practice, they are particularly popular during renovations – they can be routed in grooves without the need for expansion compensation and combine well with existing steel or copper piping through transitions.
Steel pipes (black and galvanized steel)
Steel pipes are used less frequently in new apartment buildings today, but still have an irreplaceable place in industrial installations, in larger boiler rooms and in steam pipe systems. They are joined by welding or threaded couplings. Galvanized pipes should not be used for heating today – zinc reacts with boiler inhibitors and galvanization degrades at temperatures above 60 °C. Only black or stainless steel is suitable for heating.
A detailed comparison of all materials in terms of performance, costs and suitability can be found in the article Copper, plastic or steel: a comparison of materials for heating installation.
Fittings, couplings and valves: where the most common mistakes hide
Installation fittings are the elements where the most mistakes are made in practice. The basic rule is: fittings must be made of the same material or a compatible system as the pipe. You cannot blindly combine pressed copper fittings with PEX pipes without the correct transition adapters, nor mix different manufacturers' press systems – the jaw profiles (M, V, U, TH) differ and substitution can lead to a leaky joint.
Press (crimped) fittings
They have become the standard in professional installations. They are fast, reliable and do not require an open flame – which is important during renovations in occupied buildings. Available for copper, multilayer pipes and stainless steel. Each manufacturer (Viega, Watts, Sanha, Aalberts and others) has a proprietary profile – always check the compatibility of the crimping tool with the corresponding fitting. A fitting without a correctly crimped joint may look fine at first glance, but the sealing (O-ring) is only mechanically compressed and can leak in the long term. Visual inspection is not enough – a calibrated crimping tool is necessary.
Screwed (compression) fittings
A traditional method of joining – a nut presses the olive against the pipe and seals the joint. The advantage is demountability, suitability for various materials and no need for special tools. The disadvantage is the need for precise tightening torque (not too little, not too much) and the need for occasional inspection – these joints can start to leak after years of cyclic thermal stress. Compression joints are not acceptable for underfloor heating under concrete.
Valves: ball valves, drain and air vents
Each circuit must have the possibility to be closed and drained. Ball valves with drain valves on each branch of the manifold and air vents at the highest points of the system – these are absolute minimums. Air vents come in two basic variants: manual (Schrader valve set, adjusted with a screwdriver) and automatic (float mechanism, opens when collecting air). Automatic ones are more convenient, but over time they can "weep" or crack due to impurities, so never install them in places where a dripping water drop could cause damage.
Thermal insulation of pipes: energy efficiency in practice
Thermal insulation of piping is the part of the installation that is most often underestimated or where savings are made. In numbers, this means, for example: a supply pipe DN 22 running uninsulated through an unheated basement area of 15 m in length and at a temperature of 10 °C with water at 70 °C will lose up to 80–100 W continuously by radiation – which over a heating season of 210 days represents a significant energy and financial loss.
Regulations (STN EN 12828, as well as internal regulations of apartment managers) usually prescribe a minimum insulation thickness equal to the outer diameter of the pipe in unconditioned areas. In practice, this means: for a DN 22 pipe (outer diameter ~28 mm), insulation with a thickness of 28 mm, i.e. a total diameter of the insulated pipe of ~84 mm. This is sometimes difficult to comply with in cramped installations, but any insulation is better than none.
Types of insulation:
- Foam rubber (caoutchouc) – easy installation, flexibility, available in pipe shells and tapes. Suitable for temperatures up to 110 °C. Be careful of UV degradation when exposed externally – requires cladding.
- Mineral wool (glass/stone) – resistance at high temperatures, vapor permeable, suitable for steam lines and industry. More complex installation, more expensive.
- Hard shells (FEF, PUR foam) – for rectilinear pipelines, excellent thermal insulation values.
Fastening elements and expansion compensation
Every pipe expands and contracts when the temperature changes. For plastic, the linear expansion coefficient is significantly higher than for copper or steel – for example, PP-R has α ≈ 0.15 mm/(m·K), while copper has α ≈ 0.017 mm/(m·K). In practice, this means that a 10 m PP-R pipe will extend by 75 mm – almost 8 centimeters – when the temperature changes by 50 °C. If this expansion is not compensated, it will lead to deformation or damage to the joints.
Solutions include:
- Expansion loops (U or L shapes) – the change in length is absorbed by the pipe itself during directional changes in the route. Suitable for plastic pipelines in walls and grooves.
- Axial compensators (corrugated or ring type) – inserted directly into the pipe line on long straight sections. Typically for steel and copper pipelines.
- Fixed and sliding clamps – fixed clamps secure the pipe and define the point from which the expansion is distributed to the compensating element. Sliding clamps allow axial movement but prevent lateral displacement. Proper placement of fixed points is crucial – without them, compensation does not work.
Spacing of clamps (maximum span): for PP-R DN 20, maximum 0.9 m on horizontal sections; for copper DN 22, maximum 1.8 m; for multi-layer DN 20, maximum 1.5 m. For vertical routing, the spacing is greater. These values are mandatory – non-compliance leads to pipe sagging, visual defects, and redistribution of stress on the joints.
Sealing materials: a small detail that determines everything
Sealing is an area where you can save little, but the consequences of a poor choice can be devastating. The basic rule is: never use a seal unsuitable for the given temperature or medium. Surprisingly, a large portion of heating system failures comes from exactly this – seals unsuitable for temperatures of 80–90 °C, or rubber O-rings deteriorated by chemical inhibitors in boiler water.
Overview of commonly used seals:
- PTFE (Teflon) tape – for threaded joints, resistant to temperatures up to 250 °C, chemically inert. Always wrap in the direction of the thread, at least 3 layers for DN up to 1/2", 5 layers for larger dimensions.
- Hemp fiber + sealing compound (e.g., Unipak, Loctite 55) – hemp fiber is also wrapped in the direction of the thread, sealed with a special sealing compound approved for heating (not just for cold water lines). Pastes like Unipak or Hermetik are commonly available and reliable.
- Ball seals (O-rings) from EPDM – standard for press and crimp fittings. EPDM is resistant to temperatures up to 120 °C and is compatible with inhibitors. Do not confuse with NBR (nitrile) rubbers – these are not suitable for hot water and degrade quickly.
- Flat seals – for flanges and ball valves, the material must be certified for the medium temperature. For heating, graphite, PTFE, or aramid seals are used.
A detailed overview of all seals, their uses, and specific installation techniques can be found in the article Sealing materials and fittings for heating: how to prevent water leaks.
Distributors and collectors: the heart of modern systems
A distributor (manifold) is an element where one main supply is divided into multiple smaller circuits. It is a mandatory part of every underfloor heating system and modern radiator systems with multiple circuits. The quality and correct dimensioning of the distributor directly affect the possibility of hydraulic balancing – the ability to set each circuit so that it has the same thermal output regardless of its length.
Distributors are made of brass, stainless steel, or plastic, with the number of circuits ranging from 2 to 12 and more. Each outlet should have a flow meter (rotameter) and the possibility of flow regulation. Collectors with thermostatic heads and thermostatic valves allow individual regulation of each room. The hydraulic logic of the entire system and the reasons why balancing is not an "optional" phase but a necessity are discussed in the article Hydraulic balancing of the heating system: why it is important and how to do it.
Expansion tank and safety valve: essential safety components without which it doesn't work
The expansion tank is mandatory in a closed heating system and its correct sizing is a condition for safe operation. When heating 100 liters of water from 20 °C to 80 °C, its volume increases by approximately 2.8 liters (the coefficient of thermal expansion of water at 80 °C is ~3 %). This volume must have somewhere to go – and that path is precisely the expansion tank with a membrane.
Basic sizing rule: the volume of the expansion tank should be at least 10 % of the total water volume in the system (pipes + radiators + storage tank), with the tank's pre-charge pressure set 0.2–0.3 bar lower than the static water column height of the system above the expansion tank. In practice, this means an expansion tank of 12–18 liters for a typical family house with a system content of 80–120 liters.
The safety valve (relief valve) is the last line of defense – it opens when the pressure in the system reaches the set maximum (most commonly 3 bar for low-pressure systems). The safety valve must have a discharge directed safely away from people, electricity, and heat-sensitive materials. Its discharge capacity (kW) must exceed the maximum thermal output of the source. Never block it, do not confuse it with a pressure-reducing valve, and test it regularly by manually lifting it during pressure testing.
How to choose the right materials for a specific type of installation
Theory is important, but in practice, you most often encounter a few typical situations. Here is an overview of recommended material combinations:
New construction of a family house – floor heating
Pipe: PEX-a or PE-RT with EVOH barrier, dimensions 16×2 or 17×2 mm. Manifold: brass or stainless steel with rotameters and thermoelectric actuators. Fittings: exclusively press or expansion (not threaded). Insulation: strip under the pipe in the concrete screed (to prevent heat transfer downward). Fixing: clamps or mesh at 15–20 cm intervals in curves, 30 cm on straight sections.
Apartment renovation – radiator heating
Most common choice: multilayer pipes DN 16 or DN 20, routed in wall or floor grooves. Press fittings from a compatible system. Transition fittings for connection to existing steel or copper piping. Each radiator must have a thermostatic valve and a VK valve (regulating valve on the return). Always check whether the existing expansion tank is sufficient after adding new circuits.
Boiler room – primary circuit
Copper or steel (black, welded). Thermal insulation on all pipe sections in the boiler room. Pressure gauge + safety valve + expansion tank + ball valves with drain – these are the minimum requirements for commissioning. The use of multilayer pipe in the boiler room behind the boiler is technically possible (if the temperature is up to 90 °C and pressure up to 10 bar), but I do not recommend it due to insufficient visual representation of the professionalism of the installation.
Most common mistakes when selecting and purchasing installation materials
Over dozens of projects, I have seen recurring mistakes. Listing them here is, I believe, just as important as describing what to do correctly:
- Purchase of pipe without EVOH barrier for heating – these pipes are cheaper, are sold without visible difference, but absolutely do not belong in a heating system.
- Mixing press systems from different manufacturers – different profiles, different O-ring dimensions, incompatible tool jaws.
- Underestimating thermal expansion of plastic pipes – PP-R without compensators in long straight sections is a recipe for problems.
- Use of galvanized pipe for heating – zinc reacts with corrosion inhibitors and degrades at higher temperatures.
- Omitting air vents at the tops of the route – air in the system = noisy installation + reduced radiator performance + possible corrosion degradation.
- Too small an expansion tank – the safety valve opens too often, the system operates with unnecessarily high pressure.
- Sealing unsuitable for the temperature of the medium – common rubber or NBR O-rings in hot water quickly degrade.
About the installation procedure, further professional tools and systematic execution of the installation, see the article Installation of heating systems: procedure, tools and most common mistakes.
Checklist before purchasing: what to verify
Before you order the material, answering these questions will save you time and money:
- What is the maximum temperature and pressure in my system? (Different materials for 55 °C floor heating vs. 85 °C radiator system.)
- Are the pipes routed in the ground, in concrete, in grooves, or freely in the boiler room? (Different requirements for UV resistance, mechanical protection, insulation.)
- Is it a new system, or are we connecting to an existing distribution? (Need for transition fittings, material compatibility.)
- What is the total length of the distribution and how many circuits will the system have? (Volume calculation – expansion tank sizing.)
- Does the system have oxygen inhibitors? (Compatibility of O-rings and other elastomers.)
- Is the installation within the reach of a maintenance technician or boiler room? (Accessibility for future maintenance and pressure testing – see article Pressure testing and inspection of heating installation.)
Prices and cost comparison: what plays a role in the decision
Approximate cost comparison for pipe for 100 m of distribution DN 16–22 (material only, without labor):
| Material | Pipe price (€/m, approx.) | Cost of fittings (relative) | Labor requirements | Lifespan |
|---|---|---|---|---|
| Copper DN 18 | 3.5 – 6.5 € | High | High (soldering) | 50+ years |
| Multilayer DN 16 | 0.8 – 1.8 € | Medium | Low–medium | 30–50 years |
| PEX-a DN 16 (with EVOH) | 0.6 – 1.4 € | Medium | Low | 30–50 years |
| PP-R DN 20 | 0.5 – 1.2 € | Low | Medium (welding) | 30–50 years |
| Black steel DN 20 | 1.5 – 3.5 € | Medium | Very high (welding) | 20–40 years |
From the table it is clear that the pipe itself represents only a part of the costs. Fittings, valves and labor can account for 50–70% of the total installation costs. Therefore, it is worth considering the total system cost when choosing a material – including future maintenance and possible repair costs. About what to check every season and how to prevent failures, you will read in the article Heating distribution maintenance and service: what to check every season.
Standards and regulations you need to know
Heating installation in Slovakia is primarily governed by these standards and regulations:
- STN EN 12828 – Heating systems in buildings. Design of hot water heating systems. Contains requirements for safety devices, expansion vessels, maximum temperatures and pressures.
- STN EN 14336 – Installation and acceptance of hot water heating systems.
- Decree 508/2009 Coll. (BOZP when working with pressure equipment) – applies to boilers and pressure vessels.
- NV SR No. 392/2006 Coll. – regulations for the installation of heating systems.
Do you have a question about this topic?
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