Washing machine plumbing: valves, hoses, drains and leaks

Most washing machine leaks come from three places: the fill hose, the valve it connects to, or the drain. Knowing how the machine is plumbed in makes it easier to find the leak, stop it quickly and fix the simple ones yourself. For dishwashers, see dishwasher plumbing. If the pipes bang when the machine stops filling, see noisy pipes and water hammer.

How a washing machine connects

A typical UK installation has:

• One or two appliance valves on the wall behind the machine. They are small quarter-turn taps on the hot and cold pipes, usually with a blue or red handle. They have a threaded outlet that the fill hose screws on to.
• One or two fill hoses from the valves to the back of the machine. Many machines sold now take a cold supply only. If yours has a single inlet, only the cold valve is used. Check the machine's manual.
• A drain hose from the machine into either a standpipe (an upright waste pipe with a trap at the bottom) or a spigot on the kitchen sink trap.

The appliance valves are isolation valves. Turning the handle a quarter-turn across the pipe shuts off the water to the machine without affecting the rest of the house. Our isolation valves guide explains the different types.

Before moving or working on the machine

Water and electricity are both involved, so do things in this order:

1. Switch off and unplug the machine. Only do this if the floor and the socket are dry.
2. Close the appliance valves. Turn each handle a quarter-turn so it sits across the pipe.
3. Pull the machine out gently. Do not stretch or kink the hoses, and do not drag the machine over the hoses or the drain.
4. Keep a towel and a shallow tray ready. Water stays in the hoses and in the machine's filter area.

Fill hoses

Fill hoses screw on by hand at both ends. Each end has a rubber sealing washer inside the nut. A hose usually seals by hand-tightening, because the washer does the sealing. Over-tightening with grips can crack the plastic nut or squash the washer.

Check fill hoses when you have the machine out, and replace a hose if you see:

• a bulge or blister in the hose;
• cracks, especially near the ends;
• rust or corrosion on the nuts;
• a kink that has left a permanent fold;
• any dampness at either end.

Most machines come with plain rubber or PVC hoses. Some people choose hoses with a braided stainless steel outer sheath, which resist kinking and abrasion. Whichever kind you use, the important thing is to check it and replace it when it shows wear. Hose life varies, and we do not give a fixed replacement interval. Follow the machine maker's advice.

Some machines come with an "anti-flood" or safety hose that shuts off if the inner hose fails. If yours has one, replace it with the same type from the machine maker.

Drain: standpipe or sink trap

Standpipe. The drain hose hooks over and into the top of an upright pipe with a trap at the bottom. The hose is held by a plastic crook or clip. The end should sit loosely inside the standpipe, not sealed into it, so air can get in. Push it down too far, or seal it, and the machine can siphon water out while it fills. Follow the machine maker's guidance on how far the hose goes in and how high the standpipe should be.

Sink trap spigot. The drain hose pushes on to a spigot on the side of the sink trap and is held with a hose clip. The hose usually needs to rise high under the worktop before it drops to the spigot, so dirty sink water cannot run back into the machine. A new trap with a spigot often comes with the spigot blanked off, and the blank has to be removed before use. Check the trap maker's instructions.

If water backs up into the sink when the machine empties, or the standpipe overflows, the waste pipe or trap is probably partly blocked. See blocked sink.

Backflow

A washing machine is a possible source of contamination for your drinking water, so the connection has to have suitable backflow protection. Water Regs UK says in its FAQ on appliances that "some but not all appliances incorporate backflow protection which satisfies UK requirements". If the built-in protection is not adequate, the appliance must be supplied through a separate, appropriate form of backflow protection. If you are adding a new supply for a machine, ask a plumber.

The usual leak points

Where	Usual cause	What to do
Valve to hose joint	Missing, hard or squashed washer	Close the valve, fit a new hose washer, refit by hand
Hose split or bulged	Age, kinking, damage	Close the valve, replace the hose
Machine end of the hose	Washer or cross-threaded nut	Refit squarely with a new washer
Valve body or spindle	Worn valve	Close the stopcock and replace the valve, or call a plumber
Drain hose at the spigot	Loose or missing clip	Refit the clip
Standpipe or trap	Blockage or a loose trap nut	Clear it or reseat the trap
Under the machine during a wash	Door seal, pump or internal hose	Stop using it and call the maker's engineer

Leaks from inside the machine, from the door seal, the pump or anything behind the panels, are appliance repairs. Unplug the machine and call the maker or a qualified appliance engineer.

Parts at Wickes

We haven't tested this. Figures are as the maker states them (checked 13 November 2026).

Should I turn off the washing machine valves after each wash?

Some people do, to protect against a split hose while the house is empty. It is not essential, but it is worth closing them before you go away. Make sure you can reach them easily. If you cannot, ask a plumber about moving them.

My machine fills and drains at the same time. Why?

That is often siphoning. The drain hose is pushed too far into the standpipe or sealed into it, or the standpipe is too low. Check the hose position against the machine maker's instructions.

Can I connect a washing machine to the hot supply?

Only if the machine has a hot inlet and the maker allows it. Many modern machines are cold fill only. Check the manual.