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How to plumb-in a washing machine & dishwasher

Get your new appliance set up and ready to go

Try to place your washing machine and dishwasher on a firm, level floor and close to an outside wall. Ensure that you level the appliance using a spirit level to avoid excessive vibration during use. Both these machines need a power supply as well as a water supply and a waste pipe.

How to plumb-in a washing machine & dishwasherHow to plumb-in a washing machine & dishwasherHow to plumb-in a washing machine & dishwasherHow to plumb-in a washing machine & dishwasher

Top tip

Before moving your old washing machine or dishwasher, tie or tape any loose pipes or hoses to the top so any water that’s left in them doesn’t spill all over the floor. Alternatively, drain the pipes into a bucket and remove them from the appliance.

Water supply

A washing machine is normally connected to the cold and hot water systems, but quite a few will work with just a cold supply while dishwashers usually only need a cold supply. If your machine is supplied from the pipe that feeds your kitchen tap, the water will be at mains pressure. If it also needs a hot water supply, this will be at gravity pressure from the cylinder upstairs or may be at mains pressure if heated by a combi-boiler. Most machines have a flow restrictor in the cold-water inlet to even out the pressure difference.

Safety first If you’re fitting a washing machine in your bathroom, you won’t be able to put a socket or switched fused connection unit in there. So, it’s best to mount the fused connection unit outside the bathroom and connect your machine to a flex outlet plate in the bathroom.

Power supply

Washing machines and dishwashers need to be plugged into a standard socket, but a common problem in kitchens and utility rooms is that all the sockets are positioned above the work surfaces. A good solution is to run a spur from a socket to a switched fused connection unit above your work surface, and then a cable from this to an unswitched socket below the surface to serve the machine. The connection unit should have a neon light to show when the machine is switched on.

Piped connections

If your machine’s hoses won’t reach your existing supply pipes, you’ll need to turn off your water supply at the mains tap, drain the system and cut the pipes. You can then add T-fittings and run branch pipes to the machine. These should end in mini stop valves to which your machine’s hoses can be connected. If the supply pipes run close to your machine, you can fit T-piece stop valves and screw the hoses to them. Or you might be able to use self-cutting connectors containing isolating valves, which you can install without draining the pipes. Carefully turn on the mains supply again and check for leaks.

Waste connection

Your machine’s flexible waste hose has to discharge into a waste pipe or trap above the level of the top of the drum. One option is to hook the hose into the top of an open standpipe with a P-trap at its base. From the trap, the waste pipe must run through your outside wall to a hopper head or gully, or directly into a soil stack. The air gap at the top of the standpipe will stop any dirty water siphoning back into the machine. Some manufacturers recommend a standpipe, and some water companies insist on it.

The easiest solution though, is to put your machine next to a sink and change your sink trap to a washing machine trap – which has an inlet for the waste hose above the trap. Install a non-return valve to prevent the back-siphonage of waste water; or fix a hook to the underside of the work surface and tie the hose to it, so that it runs higher than the level of the sink overflow.


Before you start, check your washing machine or dishwasher is compatible with these fittings. Connect the machine’s blue hose to the cold supply, and the red hose (if it has one) to the hot.

Step 1

To make sure you get a good seal between the connector and pipe, clean the area of pipe with steel wool and remove any paint.

Step 2

Before you fit the saddle assembly to your pipe, make sure the rubber seal is correctly positioned. Then place the backplate behind the pipe and fit the saddle over the top, aligning the screw holes. For added strength, you can screw the backplate to your wall.

Step 3

Clamp the saddle assembly in place around the pipe with its two halves square to the pipe, inserting the screws and tightening them fully.

Step 4

Make sure the valve is in the ‘off’ position, then screw it into the saddle by hand – you’ll feel it cut into the pipe as you do so. Keep turning the valve until its body is at right-angles to the pipe – this will let you turn it on and off easily.

Step 5

Secure the valve by tightening its retaining locknut with a spanner or wrench, so that the valve doesn’t move.

Step 6

Attach the supply hose to the valve by screwing its cap nut onto the threaded outlet making sure it’s tight.

Washing machine

Usually, a washing machine has hot and cold water pipes extended with T-fittings to reach its supply hoses. Mini stop valves allow you to isolate the machine without having to cut off the water supply. Hook the waste hose into a standpipe with a P-trap.


A dishwasher normally just has a cold water supply. The mini stop valve that connects the supply pipe to the machine’s hose lets you isolate the machine without turning off your water. Connect the waste hose to a washing machine trap beneath the sink or use a standpipe with a P-trap.

Top tip

Before you push your appliance back in, plug it in and run a rinse or quick cycle to check whether there are any leaks. Once you’re happy everything is watertight, position the appliance beneath your worktop. Make sure not to push the appliance back against the wall to avoid trapping the drainage hoses or damaging the water supply.

Built-in dishwashers and washing machines

If your appliance is built into your kitchen cabinets, then all the connection guidance above will still apply. The key differences are that you’ll need to secure the appliance to the cabinets and attach a decorative door to the front to match your kitchen.

Securing the appliance

Typically, the appliance will be supplied with fixing screws that go through the carcass from the inside to the worktop above and the cabinet sides. The appliance will stand directly onto the floor so adjust the legs to raise the appliance to the correct position and fix in place. If you’re attaching a plinth across the base of your cabinets, you may need to cut a groove in the top edge to allow the correct door opening.

Fixing the decorative door

The appliance should be supplied with the correct fixings to attach the door. Once attached and aligned with the rest of the cabinet doors, ensure you adjust the tension springs in the appliance carcass so that the door opens smoothly and doesn’t slam.

Top tip

If you wish to fit a 45 cm slimline appliance into a 50 cm opening in your cabinets, there’s a separate fitting kit available that allows you to secure the appliance to the cabinets centrally using the 2.5 cm spacer on either side. You can then fit a 50 cm door to the front of the appliance which neatly covers the carcass and the spacers.

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