Hep2O Push-Fit Plumbing: The Complete Guide to Fittings, Sizes, and Installation

Hep2O is Wavin's push-fit plumbing system — used extensively in new residential construction, heating installations, and renovation plumbing throughout the UK. If you've worked on a house built or refitted in the last 25 years, you've almost certainly encountered it. This guide covers the full Hep2O range at APM: the four pipe sizes, every fitting type, the demountable system that makes Hep2O a professional's tool (not a DIY shortcut), and where Hep2O fits versus the alternatives.

What Makes Hep2O Different from Other Push-Fit Systems

Hep2O and JG Speedfit are both push-fit plumbing systems and both work on the same grab-ring principle — a stainless steel collet grips the pipe on insertion, a rubber O-ring seals it. The key differences in practice:

• Hep2O is a demountable system. Every fitting can be fully disconnected using the HepKey tool — no cutting, no damage to the fitting or pipe. This is the correct choice for installations where joints may need to be accessed later: underfloor heating manifold connections, behind panels in kitchen and bathroom fit-outs, first-fix in walls before boarding.
• Pipe compatibility: Hep2O fittings accept Hep2O barrier pipe, standard plastic MLCP (multilayer composite pipe), and compatible polybutylene pipe. Always confirm pipe OD before fitting.
• Support sleeves are mandatory on plastic pipe. Unlike compression fittings, which work on copper or plastic without an insert, Hep2O requires a support sleeve inside plastic pipe at every fitting. The sleeve prevents the collet from deforming the pipe bore under pressure. This is not optional — it is the difference between a watertight joint and a slow leak behind a wall.

The Four Pipe Sizes

Hep2O covers four nominal sizes. Each corresponds to a standard metric pipe OD:

• 10mm — used for small-bore runs: underfloor heating branch pipes, secondary circuits in tight spaces. Less common in general plumbing.
• 15mm — the standard domestic size for hot and cold water, radiator connections, and branch pipework throughout a house.
• 22mm — mains supply, boiler primary flow and return, larger radiator tails, and anywhere the 15mm flow rate is insufficient.
• 28mm — high-flow applications: main boiler connections on larger systems, commercial primary circuits, thermal store connections.

Size the pipe to the flow rate required, not the existing pipework — an undersized 15mm run feeding multiple outlets will cause pressure drops that no boiler or shower pump can compensate for.

Straight Connectors

The straight connector is the core fitting — pipe to pipe, same size.

• Hep2O Straight Connector 10mm — £4.05
• Hep2O Straight Connector 15mm — £2.45 — the most-used fitting in any Hep2O installation. Keep stock on site for first-fix.
• Hep2O Straight Connector 22mm — £3.40
• Hep2O Straight Connector 28mm — £9.85

Elbows and Bends

• Hep2O 15mm 90° Spigot Elbow — £3.09 — push-fit socket one end, spigot the other. Used where the elbow needs to push directly into a larger fitting socket at one end — common at manifold connections and tank couplings.
• Hep2O 90° Elbow 22mm — £4.60 — for direction changes on 22mm supply or return runs.
• Hep2O 135° Obtuse Elbow 15mm — £3.55 — 135° bend (45° offset) for gentle direction changes. Use this to avoid a tight 90° where the pipe run needs to offset around a structural element. Produces less turbulence and pressure drop than a right-angle elbow on high-flow circuits.

Tees and Reducers

• Hep2O Equal Tee 22mm — £5.69 — three equal sockets for branching 22mm supply runs.
• Hep2O Equal Tee 28mm — £16.25 — for primary circuit branching at 28mm.
• Hep2O Reduced Branch Tee 22×22×15mm — £5.99 — 22mm run, 15mm branch. The correct fitting for dropping a 15mm radiator branch off a 22mm main flow or return. Eliminates a separate reducer at the tee point.
• Hep2O Socket Reducer 22×15mm — £3.26 — inline reducer for stepping down from 22mm to 15mm pipework.
• Hep2O Socket Reducer 15×10mm — £4.19 — for connecting 10mm underfloor heating branch pipe from a 15mm circuit.

Stop Ends

• Hep2O Demountable Stop End 15mm — £3.25 — for temporarily capping a live pipe during first-fix, or permanently capping an unused branch. Demountable — the HepKey removes it cleanly.
• Hep2O Demountable Stop End 22mm — £4.05

Tap Connectors and Iron Adaptors

Where Hep2O pipework terminates at a threaded connection — tap tails, valves, boiler connections — you need an adaptor fitting. These transition from the push-fit collet system to a BSP thread.

• Hep2O Brass Female Iron Adaptor 15mm × ½" — £6.79 — 15mm push-fit to ½" BSP female thread. For connecting to ½" threaded taps, valve bodies, and boiler connections. The brass body resists the torque of tightening a threaded connection better than a plastic fitting.
• Hep2O Bent Tap Connector 15mm × ½" — £4.65 — 90° angled version. For connections where the pipe approaches from the side and needs to turn before reaching the tap tail — common under basins and behind cisterns.
• Hep2O Socket Female Iron Adaptor 22mm × ¾" — £9.39 — 22mm push-fit to ¾" BSP female. For boiler flow/return connections and larger valve bodies.

Support Sleeves: Do Not Skip These

Support sleeves are rigid plastic inserts that go inside the plastic pipe at every Hep2O fitting. They prevent the collet from distorting the pipe bore under the clamping force, which would break the O-ring seal under pressure. Copper pipe does not need them — the copper is self-supporting. On plastic and barrier pipe, they are always required.

• Hep2O Support Sleeves 15mm, 50-pack — £31.04 — buy by the pack for any installation of scale. At approximately £0.62 per sleeve and one sleeve per pipe end at every fitting, a standard central heating first-fix through a three-bedroom house uses 80–120 sleeves.
• Hep2O Support Sleeves 22mm, 50-pack — £40.99

The HepKey Demounting Tool

• Hep2O HepKey Plus Demounting Tool 15mm, 10-pack — £4.30 — the tool that makes Hep2O demountable. Insert the HepKey collar around the pipe at the fitting, push it against the collet face to release the grab ring, and the pipe slides out cleanly. Without it, removing a Hep2O fitting risks damaging the fitting body or the pipe. One key per fitting point on a first-fix job is standard practice — leave a key at each joint for future access.

Installation Principles

Pipe preparation

Cut plastic pipe square — a deburring tool or sharp pipe slice gives the cleanest cut. An angled or burred cut prevents the pipe from seating fully in the fitting socket, causing a partial engagement that leaks under pressure. Mark the full insertion depth on the pipe with a pen before pushing home — visual confirmation that the pipe is fully seated.

Support sleeves

Push the sleeve fully into the pipe end before inserting into the fitting. The sleeve should be flush with the pipe end or just below — not protruding. A sleeve that protrudes interferes with the O-ring seal.

Pipe support

Hep2O barrier pipe has more thermal expansion than copper — allow for movement on long runs with expansion loops or offset routing. Clip or support every 500mm on horizontal runs, 800mm on vertical. Do not support so rigidly that thermal expansion has nowhere to go.

Pressure test before boarding

Always hydraulic pressure test before closing up walls or floors. Standard test: fill system, pressurise to 1.5× working pressure (typically 6–7 bar for a domestic system at 4 bar working pressure), hold for 30 minutes with no drop. Hep2O joints that aren't fully seated will show immediately under pressure — much easier to correct before the ceiling board goes on.

Quick Reference: Fitting Selection

All Hep2O fittings and support sleeves are in stock for same-day collection from our Acton trade counter. For first-fix quantities on a new build or full heating installation, call ahead and we'll pull the order.

APM Plumbing & Electrical | 24 Western Avenue, Acton, London W3 7TZ | 020 8702 8080 | apmi.uk