The free diy home improvement guide with answers to your questions on a wide range of do it yourself projects.


Washing machine or dishwasher - plumbing in

Water supply for washing machines and dishwashers

The supply of water to these is made via flexible hoses with isolating valves. These enable the machine to be moved for maintenance work. Depending on the machine, there may be cold supply only or both hot and cold.

If the machine is to be sited next to a sink or other existing plumbing installation, the supplies and waste can be branched to this relatively easily. Otherwise new pipe runs will need to be installed to the new location.

Connecting the water

fitting a T connectorSwitch off the water and drain down the pipes to which you intend making your connection. If you are branching from an existing pipe, cut the pipe and fit a "T" shape fitting. This will mean making two cuts in the pipe to make room for the fitting.

Connect the fitting (soldered or compression, depending on space and preference).

Fit a length of pipe between the "T" and the position of the new machine.

Fit an isolating valve in this branch to allow for maintenance later. Several makes of appliance connectors have integral isolating valves.

Fit a connector to the end of the pipe to which the rubber hose from the machine will fit. Check the size and thread on this before buying.

Plumbing the waste pipe

There are several options for the waste disposal from such machines. Check the manufacturer’s details for recommendations. The most common is for the flexible waste outlet to be fed into a standpipe arrangement. The diameter of the pipe should be 40 mm.

Run a waste pipe through the external wall to discharge to the drainage system.

machine trapSee waste for new appliances. This should have sufficient fall (dropping downhill) for the volume of water. This is normally recommended as 6mm per 300mm length.

Fit a deep trap to the inside end at floor level adjacent to the machine. Cut and fit a standpipe to the top of the trap. The usual length for this is 600mm from the base of the trap. Secure this, and any other pipework, with clips.

Insert the flexible waste into the standpipe by the recommended amount.

Switch on the water supply and test the plumbing.

Self boring water pipe connections

An alternative for connecting the supply pipes is to use self-boring fittings.

Check with your water supply company first as not all suppliers approve of their use.

Mount the fitting over the pipe and fix to the wall. Follow the instructions carefully regarding the assembly and alignment of components. Ensure that the valve is in the off position then insert it and screw home. Tighten the lock nut then connect the flexible hoses for the machine. Switch on the valve and check for leaks.

sponsored by

Loft Shop