How to Use Push-Fit Plumbing Fittings: Beginner's Guide

Push-fit plumbing is the easiest way to join pipes. No soldering, no heat, no compression nuts, no special skills. You cut the pipe, push it into the fitting, and it's done. These fittings are used on new-build construction sites across the UK every day — they're not a cheap shortcut. They're the standard. If you're tackling a plumbing project at home, this is where to start.

What You Need

The two main brands in the UK are JG Speedfit and Hep2O. Both are excellent. Stick to one brand per project — don't mix Speedfit fittings with Hep2O pipe or vice versa. The tolerances are matched within each brand's system.

Cutting the Pipe

Use pipe cutters, not a hacksaw. Pipe cutters make a clean, square cut in one squeeze. A hacksaw leaves a rough, angled edge that can score the O-ring inside the fitting — which means a leak.

Most barrier pipe has cut marks printed on it at regular intervals. When you're starting out, try to cut on these marks — they're spaced at the exact insertion depth of the fittings. When the pipe is fully pushed into a fitting, the nearest cut mark should just disappear inside. This gives you a visual confirmation that the pipe is fully inserted.

Why You Need Pipe Inserts

A pipe insert is a small metal or plastic stiffener that pushes into the end of the plastic pipe before you connect it to a fitting. They're included with most fitting packs, or sold separately in bags.

Never skip the insert. It does two critical jobs:

• Protects the O-ring. When you push the pipe into the fitting, the cut edge of the pipe passes over an internal rubber O-ring that creates the watertight seal. Without an insert, the sharp edge of the pipe can nick or slice the O-ring — and a damaged O-ring means a leak.
• Prevents the pipe collapsing. Plastic pipe is flexible and can be squeezed oval under the compression of the grab ring inside the fitting. The insert holds the pipe round and rigid at the connection point, ensuring a proper seal all the way around.

Push the insert into the pipe end until it's flush. It should go in with firm hand pressure — no tools needed. If it's very tight, warm the pipe end slightly with your hands.

Connecting Pipe to a Fitting

1. Cut the pipe square using pipe cutters.
2. Push an insert into the pipe end.
3. Push the pipe into the fitting until it stops. You'll feel it pass the O-ring and the grab ring. Keep pushing until it won't go any further — that's the pipe hitting the internal stop.
4. Tighten the collet (the twist collar on the outside of the fitting) until it's finger-tight. On some fittings the collet is a push-in ring rather than a twist collar — it clicks into place automatically.
5. Pull the pipe to check it's locked. It should not move at all. If it pulls out, the collet isn't engaged — push the pipe in again and make sure the collet is fully tightened or clicked.

That's it. No PTFE tape, no jointing compound, no heat, no tools beyond the pipe cutters. The O-ring inside the fitting creates the watertight seal. The grab ring (a toothed metal ring) grips the pipe and prevents it being pulled out.

How to Disconnect

Push-fit fittings are demountable — you can take them apart and reassemble them. To disconnect:

1. Loosen the collet (turn it anti-clockwise, or on clip-type fittings, push the collet ring inward towards the fitting body).
2. While holding the collet in, pull the pipe out. It should slide out smoothly.

If you're reusing a fitting after disconnecting, check the O-ring inside is still in good condition. If it looks scored, compressed, or damaged, replace the fitting. A new fitting is cheaper than the water damage from a leak.

Using Push-Fit on Copper Pipe

Push-fit fittings work on copper pipe as well as plastic. This is one of their biggest advantages — you can transition from existing copper pipework to plastic without needing a special adapter. Just push the fitting onto the copper pipe.

Two things to remember with copper

• You don't need an insert. Copper is rigid enough to hold its shape inside the fitting. Inserts are only for plastic pipe.
• Deburr the pipe end. After cutting copper with a pipe cutter, the inside edge has a raised burr. This burr can damage the O-ring as the pipe goes in. Run a deburring tool or a round file around the inside edge to remove it. Clean and smooth — same principle as preparing copper for soldering or compression fittings.

This means you can, for example, connect a push-fit fitting directly onto an existing copper pipe coming out of a wall, then run plastic pipe from there to wherever you need it. No soldering, no compression fittings, no adapters. Push on and go.

Can You Use Compression Fittings on Plastic Pipe?

Yes. Standard brass compression fittings work on plastic barrier pipe, with one rule: always use an insert. The olive compresses onto the pipe just like it does on copper, and the insert stops the pipe collapsing under the pressure.

You don't need PTFE tape on the olive when using compression fittings on plastic pipe. The olive bites into the plastic more easily than it does into copper, so the seal forms with less force. Don't overtighten — plastic is softer than copper and the olive can cut too deep if you go too hard.

Tips for a Leak-Free Installation

• Always use inserts on plastic pipe. It's the most common mistake and the most common cause of push-fit leaks. No insert = potential O-ring damage = potential leak.
• Cut square. An angled cut means the pipe doesn't sit evenly against the internal stop, and the O-ring doesn't seal evenly around the circumference. Use proper pipe cutters, not a hacksaw.
• Push all the way in. The pipe needs to go past the O-ring and grab ring and hit the internal stop. If it's only halfway in, the grab ring might hold it but the O-ring won't seal properly. Check with the cut marks — the nearest mark should just disappear.
• Count your inserts. Before you start, lay out one insert for every pipe end that goes into a fitting. At the end of the job, if there's an insert left over, you missed one. Go back and find which connection doesn't have one.
• Don't force bends. Plastic pipe is flexible but it has a minimum bend radius. If you force a tight bend, the pipe kinks and restricts flow. Use elbows or stop bends for direction changes. The pipe should curve gently, never sharply.
• Support the pipe. Clip plastic pipe to the wall or joist at regular intervals (every 300mm for horizontal runs, every 500mm for vertical). Unsupported pipe sags, puts strain on the fittings, and can pull connections apart over time.
• Don't mix brands. Speedfit pipe with Speedfit fittings. Hep2O pipe with Hep2O fittings. The tolerances are designed to match within each system. Cross-brand combinations may seal but aren't guaranteed by either manufacturer.