Washing Machine Leaking Underneath: Plumbing or Machine?

First: stop the water and make it safe

Switch the machine off at the wall socket, then pull the plug out if you can reach it without standing in water. If the socket is behind the machine and the floor is wet, turn the kitchen circuit off at the consumer unit first.

Then close the washing machine valve. It is usually a small lever valve on the pipe behind the machine, often with a blue lever for cold; turn the lever a quarter turn so it sits across the pipe. If you cannot find it or it will not shut, use the main stopcock. Mop up, then pull the machine out slowly, lifting the front slightly so the feet do not tear the vinyl or hoses.

Do not open the door of a machine that stopped mid-cycle full of water. Drain it through the pump filter into a shallow tray first, or the whole drum load ends up on the floor.

Does it leak while filling, washing or draining?

The timing of the leak points to the part responsible, so it is worth running a short rinse cycle with the machine pulled out and a torch on the back and the floor.

• Leaks the moment water starts to fill, or even when the machine is off: the fill hose, its rubber washer or the valve it screws onto. These are under mains pressure all the time the valve is open
• Leaks only while draining or spinning: the waste hose, the standpipe or sink trap it empties into, or the pump filter
• Leaks mid-wash with the door area wet: the door seal or the detergent drawer, both machine faults
• Leaks from the base with no visible source: a split internal hose, the tub seal or the pump itself, all machine faults

The plumbing side: fill hose, valve and washer

The fill hose screws onto the valve with a 3/4 inch thread and seals on a flat rubber washer inside the hose nut, not on the thread. A washer that has hardened, split or dropped out when the hose was last moved leaks as a steady drip down the back. Unscrew the hose with the valve shut, check the washer is there and flat, and replace it if it is not; hardware shops sell them in packs. Do not use PTFE tape on this joint. It stops the washer seating and can make the leak worse.

Look along the hose itself. Rubber fill hoses bulge, crack near the ends or get kinked against the wall after years of the machine walking during spin. A hose that has a bubble or a crack must be replaced, not taped: it is a burst waiting to happen, and an unattended burst fill hose can flood a floor for hours.

The valve can fail too. A self-cutting valve that has been clamped onto a copper pipe can weep where it grips the pipe, and an older valve can leak from the spindle when the lever is turned. Either needs the supply off and the valve replaced. An isolation valve that is leaking covers the different valve types and what replacing one involves.

The waste side: standpipe, sink trap and blockages

A machine pumps its dirty water out fast. If the waste pipe cannot take it away quickly enough, water backs up and overflows the standpipe or spills out of the sink trap connection, and it runs down the wall behind the machine. It looks exactly like a machine leak.

Check the waste hose is pushed well into the standpipe but not sealed into it, and that the hook on the end holds it in place. A hose sealed tight into the pipe can siphon, emptying the drum while the machine fills. Where the hose connects to a spigot on the sink trap, check the jubilee clip is tight and the hose is not split at the end.

Slow drainage is the other clue. If the kitchen sink gurgles or drains slowly, or the standpipe overflows mid-drain, the shared waste is partly blocked with lint and fat. Clearing the trap and the first run of pipe usually cures it. Leaking waste pipes explains the joints that commonly let go on this run, and a pipe leak under the sink covers the trap itself.

When the machine itself is leaking

If the hoses and waste are dry and the leak still appears, open the small flap at the bottom front of the machine. The pump filter cap behind it must be screwed fully home; after someone has cleaned the filter it is a very common cause of a puddle during the drain. Check the rubber seal on the cap for fluff and grit.

Pull the door seal back gently and look for splits, especially at the bottom where coins and underwired bras wear through it. Check the detergent drawer for a build-up of softener that makes it overflow into the cabinet. Beyond that, a leak from the pump, the tub, an internal hose or the drum bearings needs an appliance engineer or the manufacturer, not a plumber. On an older machine, get a quote before agreeing to the work: a pump is usually a modest repair, but a bearing or tub job can cost close to a new machine.

When to call a plumber and what it costs

Call a plumber when the leak is from the valve, the pipe feeding it, the standpipe or the waste run, or if the valve will not shut and the only way to stop the water is the stopcock. Typical market ranges in London, as a guide rather than our price: replacing a washing machine valve, around £80 to £150; clearing or remaking a standpipe or trap connection, around £90 to £180; fitting a new standpipe and trap where the old one was never plumbed correctly, from about £150.

A leak repairs visit starts with the £60 call-out at any hour. The engineer checks the fill and waste side, repairs what is plumbing, and tells you plainly if the fault is inside the machine so you do not pay a plumber for an appliance repair. The repair price is agreed with you on site before any work starts.