Heating and water-supply projects across Central Asia and the EAEU usually pick from four materials: PEX-AL-PEX (aluminium composite pipe), PE-Xa, PE-RT and PP-R. None of them is "best at everything" — each is optimal for a specific duty: medium temperature, working pressure, whether the system carries dissolved oxygen, and how it is joined. Below is a single comparison table and the practical stocking answer.
The four materials in one table
| Property | PEX-AL-PEX | PE-Xa | PE-RT | PP-R |
|---|---|---|---|---|
| Max continuous temp | 95 °C (peak 110) | 90–95 °C (peak 110) | 60–70 °C (Type II to 80) | 70 °C (peak 90) |
| Pressure (indicative) | PN10, ~6 bar at 80 °C | PN10 | PN10 | PN20/PN25 at 20 °C |
| Oxygen barrier | 100 % (aluminium), DIN 4726 | needs EVOH, else permeable | needs EVOH, else permeable | permeable, no barrier |
| Bending | bends and holds shape, R≈5×OD | flexible, springback, memory | very flexible, easy coil | rigid, straight lengths only |
| Joints | press/threaded, few needed | expansion sleeve or press, no fusion | press + butt/socket fusion | socket heat-fusion |
| Corrosion & scaling | none; protects system from O₂ | none (with barrier) | none | resistant, scales above 60 °C |
| Service life | ~50 years | ~50 years | ~50 years (low temp) | ~50 cold / ~25 hot |
| Price tier | medium-high | medium | low-medium | low |
| Best application | risers, mains, high-temp heating | underfloor heating, DHW, radiators | underfloor heating (UFH) | in-building cold/hot & potable water |
Pressure and temperature figures are indicative — confirm against the batch data sheet and a live quote: the real values depend on SDR, resin grade and the service (design) coefficient C.
How to read the comparison
PEX-AL-PEX — the load-bearing workhorse
The welded or seamless aluminium layer between two PEX shells makes the pipe totally oxygen-impermeable and almost non-expanding. It holds its shape after bending and does not spring back, so risers and mains need fewer elbow fittings. This is the safe choice for high-temperature heating, plant-room distribution and radiator tails, where shape stability and protection of steel equipment both matter.
PE-Xa — flexible, with memory
PE-Xa (Engel peroxide crosslinking, 70–85 % degree) is a supple pipe with a memory effect: cold-bend it with force and the wall "recovers" when heated. PE-X cannot be heat-fused, so joints use press fittings or a sliding sleeve. Without a co-extruded EVOH layer it still transmits oxygen, so closed systems must use the barrier version.
PE-RT — cheaper and repairable
PE-RT stays a thermoplastic: it can be butt- and socket-fused and is recyclable. As a low-temperature underfloor loop it is very convenient — soft and easy to unroll. For hot risers and high pressures it loses out to PEX on maximum temperature rating.
PP-R — internal water only
PP-R is rigid, supplied in straight lengths, assembled with elbows and permanent, consumable-free socket fusion. It is excellent for cold and hot water and potable supply, but not for underfloor coils: small bend radius, many joints, no oxygen barrier.
Corrosion: the oxygen, not the pipe, is what decides
All four polymers resist rust. The real risk is O₂ diffusing through the wall into a closed loop, attacking the steel boiler heat exchanger, radiators and brass valves. In sealed heating that makes the barrier more important than the pipe's raw strength: PEX-AL-PEX solves it completely, whereas PE-RT/PE-X without EVOH keep feeding the system oxygen.
Application class and service life
For hot water and heating the material is rated not just by pressure but by application class (e.g. EN ISO 15875 / 21003), which sets a 50-year temperature profile. Underfloor heating usually runs at class 4 (max 60 °C); combined supply and high-temperature heating use class 5 (up to 80 °C with 95 °C peaks). State the application class in the spec — it is the fastest way to rule out thin walls not rated for your duty cycle.
From a label to a verifiable material
"We make underfloor pipe" is not comparable information: first the material must land on a named family. PE-X by crosslinking method — PE-Xa / PE-Xb / PE-Xc, material system under ISO 15875; PE-RT under ISO 22391; PP-R under ISO 15874; PB under ISO 15876; multilayer pipe by its layer sequence (PEX-AL-PEX under ASTM F1281; non-crosslinked PE-AL-PE under ASTM F1282 — two mutually exclusive routes), with system assessment in the European framework under EN ISO 21003 Parts 1 / 2 / 3 / 5.
Four dimensions where materials really differ
- Design duty. The temperature–pressure rating and the use-condition class drive the lifetime conversion through the design coefficient; the same material carries different allowable pressures in different service classes, so an isolated "withstands 95 °C" cannot decide anything.
- Oxygen control. In closed heating loops the aluminium layer is a continuous metal barrier; co-extruded EVOH is a diffusion barrier whose effectiveness depends on the outer layer staying intact. A widely cited limit comes from DIN 4726 (current edition 2024-12): 0.32 mg/(l·d) at 40 °C, while other regulatory texts use a volume-flow basis (for example "no more than 0.1 g/(m³·d)" in a new Central Asian heating text). The units and test bases differ — the figures cannot be compared side by side. Demand standard number + test temperature + unit in one sentence.
- Dimensional stability and shape retention. A metal layer strongly reduces thermal expansion and holds bends — an advantage for risers, exposed runs and renovation; all-plastic pipe springs back but is softer and needs fewer joints in evenly buried coils. That is a difference of scenes, not a hierarchy.
- Joint system. Press, expansion, fusion and threaded each have their preconditions; multilayer pipe depends on fittings certified within the same system as the pipe. Mixing systems moves the risk into the interface, not the material.
Orientation by scene, not by ranking
| Scene | Orientation that usually holds | Must be checked |
|---|---|---|
| Wet buried residential coils | Single-layer barrier crosslinked pipe or a PE-RT all-plastic system | Use-condition class, design pressure and temperature, coil length and hydraulic calculation |
| Apartment risers, radiator tails, exposed runs | Multilayer pipe with an aluminium layer | Aluminium weld type, bending and deep-forming notes, fitting-system consistency |
| High-temperature or renovation systems | Aluminium multilayer pipe | Oxygen-permeation basis, chemical-treatment compatibility, corrosion risk of existing equipment |
| Low-temperature large areas (heat-pump ends) | Depends on the return temperature and the floor build-up resistance | EN 1264 design approach, thermal response and control needs — do not choose by material loyalty |
Polybutene (PB) is outside SANLI's documented range; PB-specific parameters and applicability must be evidenced by its manufacturer. Nothing on this page ranks one material above another — the choice follows the project design inputs and the verifiable documents.