How to install PEX pipe

Cross-linked polyethylene, or PEX, pipe has become increasingly popular in plumbing systems over the years both in hot and cold water installations. In fact, PEX pipe is gradually replacing copper pipe as it is quicker to install, does not require soldering, is more flexible and can be sealed behind a wall.

PEX pipe can be used to supply hot and cold water or to feed central heating radiators or underfloor heating systems. Extremely versatile, PEX pipe can be used for new installations, to extend existing pipe systems or to replace older pipes entirely – provided you choose the right type of pipe and pipe fittings. Affordable and easy to install, PEX pipe is an accessible and often more efficient alternative to copper pipe.

Steps

1. Connecting PEX pipe to the water supply

2. Laying PEX pipe

3. Installing PEX pipe fittings

PEX crimp fittings

PEX crimp fittings can be used to connect PEX pipe to any type of fixture. These fittings are the only type of PEX fitting that can be installed in a wall or behind a partition wall. The connection is made by compressing a crimp ring over the PEX pipe using a special PEX crimping tool. Like expansion fittings, these fittings are absolutely watertight but are permanent meaning they cannot be removed once fitted.

PEX expansion fittings

PEX expansion fittings are used to connect pipe to fixtures. They are easy and quick to assemble provided you have a special tool to briefly stretch the pipe. These fittings feature a male connection which is inserted into the expanded PEX pipe. The connection is secured by sliding a clamp ring over the male connection to trap the pipe between the two components. Much more reliable than compression fittings, the only downside of expansion fittings is that they cannot be disconnected once in place.

PEX compression fittings

PEX compression fittings can be used to connect PEX piping or to connect PEX pipe to other types of pipe like copper. These fittings are compressed by tightening a compression nut or ring around a compression insert using an open ended spanner or adjustable spanner. They are quick to fit. These fittings can be used for cold or hot water systems and tend to be the most straightforward of all PEX fittings to install.

Connecting to mains water

All plumbing installations, no matter the type, start with the mains water supply. Your local water company sets you up with a water supply pipe and may also fit a water meter and pressure reducing valve.

This external supply pipe runs to your internal supply pipe which feeds all the hot and cold water systems in your home. A manifold may be fitted to run pipes to various appliances. You will usually need PEX crimp or expansion female couplers to run pipe from a manifold.

Do not forget that before working on any plumbing system, it is important to cut off the water at the mains using the shut-off valve located before or after the water meter.

Installing hot or cold PEX pipe

It's fairly straightforward to tell the difference between different PEX pipes since they are different colours:

• blue is for cold water;

• red is for hot water.

If the pipe is buried it should be inserted in conduit. It is possible to buy PEX pipe in conduit.

PEX pipe markings

PEX pipe comes in three basic types depending on the cross-linking method used to make it:

• PEX-a: Pipe is cross-linked using the 'Engel' process which means Cold Expansion PEX (CEP) fittings can be used.

• PEX-b: Cross-linking using the silane method.

• PEX-c: Cross-linking by electron beam or gamma radiation.

PEX pipe used to feed hot water systems should be pre-insulated. Don't forget that any connections located within or behind walls should be secured with crimp fittings.

PEX pipe sizes

* Oxygen-barrier PEX pipe should be used for underfloor heating systems to prevent algaie and bacteria growth in the pipe.

Once your hot and cold PEX pipe is in place, you will need to choose the right fittings depending on the installation. Only PEX crimp fittings can be fitted behind or within walls. They are therefore perfect for installing a kitchen sink, basins or shower. Remember that for sanitaryware with hot and cold feeds, the hot water should always be on the left.

For other installations, choose PEX expansion fittings for a more reliable connection than compression fittings.

If you are installing PEX pipe without a wall mount fixing kit (for a bath, for example), you can use wall plate fittings to create an additional anchor point for your pipe.

Required skills

Installing PEX pipe does require basic plumbing skills. Knowing how to choose the right type of PEX pipe is essential. You will also have to choose the right size depending on the type of installation you are plumbing in. When it comes to junctions and connections, you will need to know how to fit different types of accessories and have the right tools to do so (e.g. expansion tools, crimping tools, pipe cutters, and so on).

No matter the type of system you are installing (e.g. a new system, renovation or extension), it's important to be meticulous when laying pipes (visible or hidden) and fittings (expansion, crimp, compression, etc.). It will also be necessary to use a drill or hammer drill. It's also useful to have experience plastering, filling or even pouring concrete in order to carry out tasks like pouring concrete over pipes or filling in chases.

Personal protective equipment (PPE) is required to help you work safely.

Time required

Several hours to several days depending on the type of system you are installing

Number of people required

1 or 2 people (depending on type, size and length of installation)

Tools and equipment

• Pipe cutter

• Pipe wrench

• PEX expansion tool

• Crimping tool

• Flaring tool

• PE pipe deburring tool

• Lubricant