Hep2O Push-Fit Fittings: The Trade Guide to Barrier Pipe and Speed-Fit Plumbing

Hep2O Push-Fit Fittings: The Trade Guide to Barrier Pipe and Speed-Fit Plumbing

Hep2O is the UK trade standard for push-fit plastic plumbing in heating and hot/cold water systems. Made by Wavin, it has been on the market for decades and is stocked by every plumbers merchant worth visiting. Push-fit systems like Hep2O are the fastest way to run pipework — no flux, no torch, no solder, no WRAS-approved jointing compound. Push the pipe in, it grips. This guide covers barrier pipe, fitting types, temperature ratings, and the one thing that trips people up: where push-fit should not be used.

How Push-Fit Works

A push-fit fitting contains a stainless steel grab ring and an EPDM O-ring seal. When the pipe is pushed in past the O-ring, the grab ring bites into the pipe surface and locks it in place. Pulling the pipe back simply tightens the grab ring further — the harder you pull, the tighter it grips. To release a demountable fitting, you press the release collar inward while withdrawing the pipe.

The key requirement: the pipe end must be cut square with a pipe slice or cutter (not a hacksaw, which leaves burrs), deburred, and marked at the insertion depth before jointing. An under-inserted pipe — one that hasn't reached the full depth — will weep under pressure. Mark the depth, push to the mark, confirm the mark is flush with the fitting face.

Barrier Pipe: What It Is and Why It Matters

Standard plastic push-fit pipe (without a barrier layer) is oxygen-permeable. Over time, dissolved oxygen permeates through the pipe wall into the heating system water, accelerating corrosion of steel components — boiler heat exchangers, radiators, and pump bodies. This causes black magnetite sludge, blockages, and premature failure of expensive components.

Barrier pipe has an aluminium or EVOH (ethylene vinyl alcohol) layer laminated into the pipe wall that blocks oxygen diffusion. For central heating systems — any pipework that connects to radiators, a boiler, or an underfloor heating manifold — barrier pipe is required. Using non-barrier plastic pipe in a closed heating system is poor practice and can invalidate boiler warranties.

For cold water supply and hot water domestic pipework (not connected to the heating circuit), standard non-barrier plastic pipe is acceptable — but using barrier pipe throughout causes no harm and simplifies stock management.

Hep2O barrier pipe is white with a silver stripe identifying the barrier layer. Non-barrier is plain white. Check before cutting from coil.

Sizes: 15mm, 22mm, and 28mm

Hep2O is available in three main sizes for domestic and light commercial use:

• 15mm — domestic distribution, radiator connections, tap feeds, basin and bath supplies. The most commonly used size.
• 22mm — main distribution runs, boiler flow and return, bath feeds, high-flow shower supplies.
• 28mm — primary circuit on larger systems, commercial DHW distribution.

Pipe is available in straight 3m lengths or coiled (15mm in 25m and 50m coils, 22mm in 25m and 50m coils). Coiled pipe is faster for long runs but may require warming in cold weather to straighten for fitting insertion — cold plastic is stiffer and harder to push fully home.

Fitting Range

The Hep2O fitting range covers all standard configurations:

• Straight connectors — joining two lengths of pipe, in-line repairs
• 90° elbows (standard and spigot) — changes of direction; spigot elbows push directly into manifolds or clip systems
• Equal tees and reduced tees — branch connections; reduced tees (22mm x 22mm x 15mm, 22mm x 15mm x 15mm) avoid the need for a reducer at the branch
• Stop ends (demountable) — temporary capping during installation, or permanent end stops; demountable versions can be removed for future extension
• Brass adaptors (female BSP) — transition to threaded fittings, tap connections, appliance feeds
• Bent tap connectors — 90° transition from 15mm pipe to 1/2" BSP at the tap tail

Temperature and Pressure Ratings

Hep2O push-fit fittings are rated for:

• Temperature: 0–95°C continuous service
• Pressure: 10 bar at 20°C; lower at elevated temperatures (check manufacturer data for the precise rating curve at 95°C)

For normal domestic CH systems (typically 1.5–3 bar working pressure, 80°C flow temperature), Hep2O comfortably exceeds requirements. For unvented hot water systems, confirm the working pressure does not exceed the fittings de-rated pressure at the operating temperature.

Where Not to Use Push-Fit (Without Precautions)

Push-fit should not be used:

• Within 1.5m of the boiler heat exchanger outlet — the temperature can briefly exceed 95°C during ignition. Use copper soldered or copper compression for the first metre, then transition to push-fit.
• Concealed within walls without a duct — any concealed plastic pipework should be sleeved so it can be withdrawn and replaced without opening walls. Push-fit joints concealed in walls must be accessible.
• Where mechanical stress is applied — push-fit is not designed for pipework that is subject to vibration or movement. Use brackets at correct centres (every 300mm for 15mm horizontal runs) to prevent stress at joints.

Products We Stock

We hold the Hep2O barrier pipe and fitting range in 15mm and 22mm at our Acton branch. Same-day collection from 24 Western Avenue, Acton W3 7TZ. Call 020 8702 8080.

• Hep2O 15mm x 3m Barrier Pipe
• Hep2O 15mm x 25m Barrier Pipe Coil
• Hep2O 22mm x 3m Barrier Pipe
• Hep2O 22mm x 25m Barrier Pipe Coil
• Hep2O 15mm 90° Spigot Elbow
• Hep2O 22mm x 22mm x 15mm Reduced Tee
• Hep2O 15mm x 1/2" Brass Female Adaptor
• Hep2O 15mm Demountable Stop End

Browse the full range: Hep2O Push-Fit Fittings at APM | Plumbing Fittings