Summary

Push-fit plastic plumbing displaced compression and end-feed copper for a generation of UK domestic work because it's faster, doesn't need a flame, and is more forgiving in cold or wet conditions. The three brand names — JG Speedfit (Reliance Worldwide), John Guest (parent brand of Speedfit, now also part of RWC), and Hep2O (Wavin) — have become genericised: builders say "I'll Hep it" or "Speedfit it" the way they say "I'll Hoover the floor."

But the systems are not identical and they are not officially compatible with each other. Pipe outside diameters are nominally the same (10, 15, 22, 28 mm), but tolerances and wall thicknesses differ between PE-X (polyethylene cross-linked) and polybutylene, and the collet/grab-ring geometry inside each brand's fitting is tuned to that brand's pipe. The manufacturers will sell you a brass insert or compatibility adapter, but their warranties strictly apply only to all-own-brand systems.

The other common misconception is that push-fit fittings are universally demountable. Speedfit and JG fittings can be released by pushing in the collet and pulling the pipe out — but the collet release on Speedfit needs a dedicated tool for fittings in tight spaces. Hep2O Smart Sleeve fittings can be released without a tool by twisting the body. None of the systems should be repeatedly demounted in the same joint without inspection — the O-ring takes a set and the grab ring can score the pipe.

Key Facts

Brand families

Standards and approvals

Pressure and temperature ratings (typical)

These are typical published figures; the binding values are on the manufacturer's data sheet for each specific fitting size and class.

Pipe materials

Demountability

Insert requirement

All three brands require a stainless steel or brass pipe insert pushed into the cut end of the pipe before insertion into the fitting. The insert:

  1. Holds the pipe round (so the O-ring seals properly).
  2. Reinforces the pipe wall against grab-ring damage.
  3. Is colour-coded by pipe size (10 / 15 / 22 / 28 mm).

Forgetting the insert is the single most common cause of push-fit joint failure. A pipe inserted without a sleeve will oval under pressure, the O-ring will leak, and the joint will eventually pull out. Inserts are cheap (pence each) — buy in bulk.

Warranties

Mixing brands voids the warranty (in principle — see compatibility section below).

Where each is preferred

Quick Reference Table

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Property JG Speedfit John Guest Hep2O
Pipe material PE-X / polybutylene PE-X / polybutylene Polybutylene
Pipe colour White (PE-X) or grey White / clear Grey
Insert required Yes Yes Yes
Demountable tool-free No (push collet) No (push collet) Yes (twist sleeve)
Cold max pressure 10–12 bar @ 20°C 10–12 bar @ 20°C 10 bar @ 20°C
Hot max continuous 6 bar @ 60°C / 3 bar @ 82°C 6 bar @ 60°C / 3 bar @ 82°C 6 bar @ 60°C / 3 bar @ 82°C
Heating circuit (95°C peak) Yes (Class S) Yes (Class S) Yes (Class S)
Warranty 25–50 yr (all-Speedfit system) 10–25 yr 50 yr (all-Hep2O system)
Sizes 10 / 15 / 22 / 28 mm 10 / 15 / 22 / 28 mm 10 / 15 / 22 / 28 mm
WRAS approved Yes Yes Yes
BS 7291 compliant Yes Yes Yes
Typical retail price (15 mm elbow) £1.20–£1.80 £1.50–£2.20 £1.40–£2.00

Detailed Guidance

Cross-brand compatibility

The manufacturers' official position is: don't. In practice, the outside diameters of 15 mm, 22 mm and 28 mm pipe across all three brands are within tolerance of each other, and a Speedfit fitting will accept Hep2O pipe (and vice versa). The grab ring will engage, the O-ring will seal, and the joint will hold under domestic test pressures.

The problems are:

  1. Warranty — using mixed-brand systems voids both manufacturers' warranties. If a joint fails and floods a customer's kitchen, neither manufacturer will pay out.
  2. Polybutylene vs PE-X surface hardness — slightly different stiffness can affect grab-ring grip in marginal joints. PB is softer; PE-X is stiffer.
  3. Insert compatibility — Hep2O inserts are sized for PB pipe; Speedfit PE-X inserts are sized for PE-X. Using a Hep2O insert in PE-X (or vice versa) can result in a sloppy fit.
  4. Long-term creep — over 25+ years at elevated temperatures, mixed systems may behave differently to all-own-brand systems. There's no field data.

If you have to bridge brands, use a brass compression fitting or a manufacturer's "transitional" fitting (e.g. an end-feed solder onto copper, then a fresh push-fit onto the new brand) — anywhere both sides can be inspected if there's a future leak.

Connecting to copper

All three brands have fittings designed to push onto copper pipe (15 / 22 / 28 mm), as long as the copper is clean, deburred, and the correct OD. Copper is harder than plastic, so the grab ring grips better — but copper expansion/contraction is different to plastic, so transitions from copper to plastic via push-fit are a slight risk on long heating runs. Use compression or end-feed for the changeover where you can.

When pushing a fitting onto copper:

  1. Cut square with a wheel cutter (not a hacksaw).
  2. Deburr inside and out.
  3. No insert needed (copper is already round and stiff).
  4. Push in fully — the fitting body should sit against the depth mark you've made on the pipe.
  5. Tug to check engagement.

Insert procedure for plastic pipe

Push-fit insert checklist:
1. Cut pipe square with a plastic pipe cutter
2. Deburr the inside lightly (a Stanley blade is fine)
3. Mark the depth of insertion on the pipe (use the fitting body — typically 25 mm for 15 mm pipe)
4. Insert the stainless steel insert FULLY into the pipe end (it should sit flush)
5. Push pipe into fitting up to the depth mark in ONE motion
6. Tug the pipe firmly to confirm grab-ring engagement
7. If pulling out: cut pipe back past the grab-ring marks before re-using

Pipe support and clipping

Plastic pipe needs more frequent support than copper because it's more flexible and expands more with temperature. Typical support spacings (BS 7291 / manufacturer):

Use plastic pipe clips (which allow the pipe to slide as it expands) — not metal clips that bite into the pipe. Avoid running plastic pipe across the underside of joists without support; it will sag and cause flow noise.

Expansion allowance

Polybutylene and PE-X expand about 0.15 mm per metre per °C — roughly 12× more than copper. On a 10 m hot run going from 20°C cold to 70°C hot, the pipe will grow about 75 mm. Allow for this with expansion bends, clip the pipe so it can slide where straight, and don't fix it rigidly at both ends of a long run.

Heating circuit considerations

All three brands are rated for primary heating circuits (Class S, 95°C peak). However:

  1. The pipe MUST have an EVOH oxygen barrier (HepFlow, Speedfit Barrier Pipe). Non-barrier pipe lets oxygen diffuse in and accelerates rust in the boiler heat exchanger and steel radiators.
  2. Boiler manufacturers typically require a minimum 0.5 m or 1 m length of copper directly off the boiler flow and return before transitioning to plastic, to handle the highest temperatures and to provide a fire-safe length around the boiler.
  3. Direct cylinder primary connections (heating coil) — check the cylinder manufacturer's instructions; many still require copper or steel within 1 m of the cylinder.

Common failure modes

Frequently Asked Questions

Can I use a Speedfit fitting on Hep2O pipe in an emergency?

Mechanically yes — it will hold under domestic pressures. Officially no — both warranties are voided. If you have to do it as a temporary fix, plan to redo it with matched components within a few days. Don't bury a mixed-brand joint in a wall or under a screed.

Why does my push-fit joint leak at the threaded end (the side that screws onto a valve)?

Almost always insufficient PTFE tape (or no tape) on the male thread. Push-fit fittings rely on PTFE or jointing compound on the thread side, exactly like compression fittings. Wrap 8–10 turns of PTFE clockwise around the male thread before screwing in. The push-fit side seals on the O-ring; the threaded side seals on the tape.

Do I really need a stainless steel insert, or can I skip it?

Yes you need it. Without it, the pipe will oval under pressure and the O-ring will leak (slowly at first, fast later). Inserts cost pennies; never skip them. The only exception is when pushing onto copper pipe — copper is already round, no insert needed.

How long do these systems actually last?

Manufacturers warrant 25–50 years. The first generations of UK push-fit systems are now 30+ years old and field experience is broadly good — failures are rare and almost always traceable to installation defects (no insert, not pushed home) rather than the system itself. The published ageing data suggests 50 years at typical UK domestic temperatures and pressures is achievable.

Can I use push-fit on the mains supply (incoming from the meter)?

Up to the first stop valve, the mains supply is the responsibility of the water company and must be MDPE (blue plastic) or copper per the water company's spec, not push-fit. After the stop valve, push-fit is fine. Some installations now use push-fit straight after the stop valve; others prefer to keep the first metre in copper as a robustness measure. Either is acceptable.

Are these systems noisier than copper?

Marginally. Plastic transmits less mechanical noise but expansion/contraction creaks are more noticeable than with copper. Long unclipped runs tick as they warm up. Good support and expansion allowance (see above) minimise this.

Regulations & Standards