Washing Machine and Tumble Dryer Valve and Waste Installation

If the wall already has water and waste outlets, the job is fairly quick. If the pipes need extending or rerouting, the plumber has more to do: cutting channels, running new pipe and making good the wall afterwards. A typical sequence looks like this:

1. Turn off the main water supply to the flat or house and release the pressure from the pipes.
2. Mark the position of the valve and waste to suit the appliance and the manufacturer's instructions.
3. Prepare the water outlet and the waste outlet. New waste pipe needs a steady fall towards the soil stack.
4. Fit the valve to the water outlet and seal the thread with PTFE tape or hemp and paste, depending on the type of joint.
5. Fit the trap: either a recessed trap set into the wall or a surface-mounted trap on the waste outlet.
6. Connect the washing machine's fill hose to the valve and push the drain hose into the trap.
7. If the dryer has a condensate drain, connect it to the second inlet of the same trap.
8. Turn the water back on, check for leaks and run a test cycle that includes draining.

Why does a tumble dryer usually not need its own valve? Condenser and heat pump dryers only get rid of water. They do not take any from the mains. Vented dryers need neither water nor waste, only a vent to the outside. Only some models with a steam function need a water supply, so check the manual before the plumber arrives.

Valve

• Lever ball valve: simple and reliable, and one movement shuts the water off. For washing machines it usually has a 3/4" male thread, so the hose screws straight onto it.
• Valve with backflow protection: this stops water from the machine being drawn back into the drinking water supply. It is a sensible choice, and many washing machine valves have it built in.
• Combination valve: it has two outlets, for example one for the washing machine and one for the dishwasher. It saves space under the worktop.
• Flood protection valve: it closes itself if the hose bursts or water escapes. It is especially useful in flats, where a leak ends up in a neighbour's ceiling.

Choose brass or nickel-plated brass. Plastic valves on a pressurised supply tend to be less durable, and their threads damage more easily.

Trap

• Recessed trap: it sits inside the wall, so nothing sticks out behind the machine and the appliance can go closer to the wall. It is easiest to fit while the wall is being tiled or plastered.
• Surface-mounted or standpipe trap: it goes onto an existing waste outlet and fits quickly. It suits a utility room or a later installation.
• Dual-inlet trap: it takes the washing machine and the dryer's condensate drain, or the washing machine and the dishwasher, at the same time.

A good trap holds a water seal against smells and has a non-return flap that stops water coming back from the drain. You should also be able to clean it without opening up the wall.

You need to be able to reach the valve. If it sits low behind the machine near the floor, you will not get to it in an emergency. It usually goes above the level of the machine's worktop, or somewhere you can reach with the appliance pushed in. That is often roughly one metre from the floor.

For the waste, follow the manufacturer's instructions. Most washing machines want the end of the drain hose at roughly 60 to 100 cm above the floor. If the waste is too low, water can siphon out of the machine during the wash. If it is too high, the pump struggles and the machine shows a drain error. The waste pipe is usually 40 mm or 50 mm in diameter and needs a fall towards the stack.

The electrical socket is not part of this job, but its position matters. In bathrooms and utility rooms a qualified electrician should install and connect the socket to the local wiring regulations, with RCD protection. Keep the valve and trap away from directly above the socket.

The job is quick and simple when working water and waste outlets are already in the right place and only the valve and trap need fitting. It takes more work in these situations:

• There are no outlets, and they have to be run from the nearest supply pipe or stack.
• Old steel pipes are corroded or furred up, and the thread may crack when the old valve comes off.
• The machine moves further from the stack, and the waste cannot get enough fall.
• The wall is tiled, and the outlet has to be made good without damaging the tiles.
• The water cannot be shut off for one flat alone, so the whole riser has to be closed.

In a block of flats, agree any work on the riser, or any shutdown that affects other flats, with the building management or owners' association. If the renovation changes the bathroom layout, check with the local building authority whether you need approval or a notification.

• Valve hidden behind the machine: in practice it often happens that nobody has closed the valve for years, and in an emergency nobody can find it.
• Hose hooked loosely over the edge of the bath or basin: the hose moves during draining and the water ends up on the floor.
• No trap, or a hose pushed too deep into the waste: drain smells come back into the room, and the machine can draw dirty water back in.
• Waste at the wrong height: the machine either empties itself or reports a pump error.
• Kinked or stretched fill hose: sooner or later it bursts, usually at the bend.
• Too much PTFE tape or hemp: the valve can crack when tightened, or the joint leaks from the start.

If the water and waste outlets are already in the wall and you only need to replace an old valve and fit a trap, you can do it yourself. Leave new pipework, work on the riser and anything electrical to professionals.

1. Turn off the main water supply and open the nearest tap to release the pressure.
2. Put a cloth and a container under the outlet to catch any remaining water.
3. Undo the old valve with a spanner while holding the outlet with a second spanner so it does not twist in the wall.
4. Clean old hemp and dirt out of the outlet's internal thread.
5. Wrap PTFE tape, or hemp and paste, around the new valve's thread in the direction of the thread.
6. Screw the valve in by hand, then tighten it with a spanner so the lever ends up pointing forwards or upwards.
7. Fit the trap to the waste outlet and hand-tighten the nut.
8. Connect the fill hose with its rubber washer and push the drain hose into the trap.
9. Open the main supply slowly and check the joints for a few minutes with a dry paper towel.
10. Run a short programme that includes draining, and check the trap and hoses.

At handover, take a few minutes to check the following:

• The valve opens and closes easily and you can reach it with the appliance pushed in
• The valve, hose and trap joints stay dry after several minutes under pressure
• For new pipework, the plumber has done a pressure test and confirmed it to you
• The waste height matches the washing machine manufacturer's instructions
• The drain hose sits firmly in the trap and does not move during draining
• No water overflows during draining and there is no smell from the waste
• The fill hose is neither kinked nor stretched
• If you use the dryer's condensate drain, it is connected to the trap and not left loose
• The wall around the outlets is made good and the tiles are undamaged