- PEX-AL-PEX (multilayer pipe)
- Five layers: PE-X / adhesive / welded aluminium / adhesive / PE-X. The aluminium layer gives a 100% oxygen barrier, low thermal expansion and shape retention. Standards: EN ISO 15875, GOST R 52134.
- PE-RT (polyethylene of raised temperature)
- Thermoplastic polyethylene; heat-fusible and recyclable, very flexible and easy to coil — cost-effective for low-temperature underfloor heating. Standards: EN ISO 10508 / GOST 32415.
- PE-Xa / PE-Xb (cross-linking method)
- Distinguished by cross-linking method: PE-Xa is peroxide (Engel) cross-linked (~70–87% degree, with a memory effect), PE-Xb is silane cross-linked. Cross-linking raises heat and pressure resistance but rules out heat fusion — use press or slide-sleeve joints.
- EVOH (oxygen-barrier layer)
- An ethylene-vinyl alcohol layer co-extruded onto the pipe wall to stop oxygen diffusing into closed heating systems, meeting DIN 4726; usually covered by a protective outer layer.
- DIN 4726
- The German standard limiting oxygen permeation through plastic heating pipe (to roughly <0.325 g/m³·day) so that steel and copper components in the system are protected.
- PN (nominal pressure)
- Nominal Pressure — the design working-pressure class referenced to 20 °C (e.g. PN10, PN20). The allowable pressure falls as temperature rises and must be derated for the duty.
- SDR (standard dimension ratio)
- The ratio of outside diameter to wall thickness (SDR = dn/en). A lower SDR means a thicker wall and higher pressure rating; SDR and PN together set the rating.
- Press fitting / slide sleeve
- A stainless-steel or brass fitting compressed cold with a dedicated tool to form a seal — no heat fusion required; the standard jointing method for PEX and PE-RT.
- Manifold
- A brass or stainless-steel assembly that distributes the heat-transfer fluid to the heating loops and collects the return, often with flow balancing and thermostatic heads.
- Oxygen corrosion
- Oxygen diffusing through the pipe wall into a closed loop corrodes the boiler heat exchanger, steel radiators and brass parts — a leading cause of wet-system failure. An oxygen barrier largely prevents it.
- GOST / EAC certification
- EAC (the TR CU conformity mark) is the mandatory certification for the Eurasian Economic Union market (Russia, Kazakhstan, Belarus, etc.); GOST is the CIS/Russian national standards system. Pipe sold into the Russian-speaking market generally needs EAC.
- CE marking / EN standards
- CE is the EU conformity mark; EN standards (e.g. EN ISO 15875, EN 12164) set European material and dimensional requirements — relevant when supplying EU-facing markets.
- Linear thermal expansion
- How much a material lengthens per degree (mm/m·K). Thanks to the aluminium layer, multilayer pipe expands far less than plain PE; design must allow expansion loops or anchors accordingly.
- Coil / straight length
- Coils supply continuous metres, cutting the number of loop joints; straight lengths (bars) suit rigid materials like PP-R. Small-diameter multilayer and PE-RT typically come in 100–500 m coils.
- MOQ (minimum order quantity)
- The smallest quantity a factory will accept, often counted as metres per diameter or cartons per model; the MOQ for OEM/private-label is usually higher than for standard wholesale.
- Incoterms (FOB/CIF/DDP)
- ICC-defined trade terms setting out transport, insurance and where risk passes between seller and buyer: FOB (at origin), CIF (to the destination port, freight & insurance included), DDP (delivered duty paid). Always state the term on a quote.
- HS code 3917
- The Harmonised System heading for tubes and fittings of plastics; PEX-AL-PEX and PE-RT usually fall under heading 3917, with country-specific subheadings and duty rates — verify before clearance.
- Nominal OD (dn) / wall thickness (en)
- dn = nominal outside diameter, en = nominal wall thickness (e.g. 16×2.0, 20×2.0, 26×3.0 mm); together they set the bore, SDR and pressure rating. Underfloor heating commonly uses 16×2.0; risers use 20×2.0 / 26×3.0.