Copper vs Plastic Pipes: Which Should You Use?

Both copper and plastic pipe are fine for household water and central heating when the right product is fitted properly, so the honest answer to "which is better?" is that it depends where the pipe is going. Copper is rigid, takes heat and sunlight, resists rodents and looks tidy on show, which is why it's used for exposed runs and at the boiler. Plastic is flexible, so long runs under floors need fewer joints, and it doesn't corrode, but it has to be installed with the correct inserts and clips and kept out of sunlight. Most homes that have had any work done in the last twenty years already have both.

Copper vs plastic at a glance

Whatever the material, the Water Fittings Regulations require pipes and fittings to be watertight, adequately supported, protected from frost and suitable for the pressure and temperature they'll see. Using products tested for drinking water, such as those listed by WRAS, is the usual way to show they're suitable.

Where copper is the better choice

• At the boiler. Many boiler manufacturers specify copper for a length of pipe from the boiler connections, because of heat and to keep the pipework rigid. The rule and the distance vary by make, so the installation manual is the reference.
• Exposed runs. Pipes along skirtings, up walls, in airing cupboards and around the cylinder look neater in copper and are less likely to be knocked or pulled.
• Outside and in lofts with daylight. Plastic degrades in sunlight, so exposed external pipework and outside taps are normally copper, lagged against frost. See our guide to stopping pipes freezing.
• Where rodents are likely. Under suspended floors in older London houses, mice and rats can gnaw plastic pipe.
• Gas. Gas pipework inside the home is copper or steel and is a job for a Gas Safe registered engineer only.

Where plastic makes sense

• Long runs under floors. A single length can be threaded between joists with no joints in the hidden section, which is where leaks are hardest to spot.
• Awkward routes. Plastic bends round obstacles and through notched joists more easily than copper, so it's popular for new radiator circuits, bathroom refits and extensions.
• Where noise matters. Plastic doesn't transmit ticking and knocking the way copper does. If you have banging pipes, though, the cause is usually pressure or loose clips; see our guide to water hammer.
• Frost resistance. Plastic pipe tolerates freezing better than copper, which can split. It should still be insulated, because a frozen pipe of either type stops the water.

Plastic has rules of its own. It needs a metal pipe insert wherever it goes into a compression fitting, closer clip spacing than copper so it doesn't sag, and protection from screws and nails where it runs under floors or behind boards. For heating, use barrier pipe designed for heating systems.

Joints: soldered, compression and push-fit

Most leaks happen at joints rather than along the pipe, so the fitting matters as much as the pipe.

• Soldered (end-feed or solder-ring): copper only. Neat, compact and permanent. It needs a blowtorch, so care is needed near timber and wiring, and the flux has to be cleaned off afterwards.
• Compression: works on copper, and on plastic with an insert. A brass nut squeezes an olive onto the pipe. It can be taken apart and remade, which is why isolation valves and appliance connections use it. Over-tightening distorts the olive; under-tightening weeps.
• Push-fit: works on copper and plastic. Quick and tool-free apart from a cutter, and useful in tight spaces. The pipe must be cut square, deburred, inserted to the full depth and, on plastic, fitted with an insert. Push-fit joints are bulkier than solder and shouldn't be buried where they can't be reached.

If a joint is already leaking, turn the water off and see our guides to a cracked or leaking pipe and leaking pipes.

How long do copper pipes last?

There's no fixed lifespan for copper pipe. Pipework put in decades ago is often still perfectly sound, and age on its own isn't a reason to replace it. Copper usually fails for a specific reason:

• Pinhole corrosion, a tiny leak through the pipe wall, sometimes linked to water chemistry, flux left inside after soldering, or very high flow speeds.
• Frost. Water expands as it freezes and can split copper, especially in lofts, garages and outside walls. Our frozen pipes guide covers what to do.
• Physical damage from nails, screws, floor fixings or pipes that have rubbed against masonry.
• Poor original joints that were never quite right and eventually weep.

Green deposits on the outside of a joint, damp patches that come and go, and one pinhole leak after another on the same run are the signs that a section is worth replacing rather than patching again. Our pipe replacement service covers renewing a section or a whole run.

Mixing copper and plastic safely

Joining copper to plastic is routine: a push-fit fitting, or a compression fitting with an insert in the plastic side, does the job. Two things are easy to miss:

• Electrical bonding. Metal water and gas pipes are often part of the home's main bonding, and a section of plastic breaks that metal path. If you're replacing copper with plastic, especially near where the pipes enter the building or in a bathroom, have an electrician check the bonding is still correct.
• The boiler end. Keep to whatever the boiler manufacturer specifies for pipework at the boiler, and don't put plastic where it could be exposed to flue heat.

Lead and galvanised pipes

If you find dull grey, soft pipe with bulbous joints, it's probably lead, which is common in older London houses on the supply pipe or rising main. Lead can leach into drinking water, so it isn't used for new water pipework, and replacing it is worth doing whether you choose copper or plastic for the new section. See our lead pipe replacement service. Old galvanised steel pipe rusts from the inside and restricts flow, and is also normally replaced rather than extended.

We replace and reroute pipework across London, choosing copper or plastic for each section rather than one for everything. Labour is £95 an hour, the £60 call-out is waived when the job runs over 2 hours, materials are at trade cost with no markup, and we confirm the price before any work starts. If you're moving a radiator at the same time, see what it costs to move a radiator.

Frequently Asked Questions