Why is my dishwasher leaking?

Where the water appears tells you which of six things is leaking — front, underneath, at the back or only during fill each point at a different part.

Difficulty: beginner
Time: 1 hr
Read: 5 min
Safety: warning

Short answer

Note exactly where the water appears and at what point in the cycle. Water at the front of the door is a seal or an overfill; water from underneath at the back is the inlet or drain hose; water underneath at the front is the door seal or the tub. Turn it off at the socket and the isolating valve before you investigate.

A dishwasher has three separate water paths — the incoming supply, the recirculating wash, and the drain — plus a door that has to seal against a tub full of moving water. Each one leaks in a characteristic place, so the location and the timing between them narrow it down quickly. Guessing wastes an afternoon; watching one cycle with a torch usually does not.

Safety

Switch the machine off at the socket and turn off the appliance isolating valve before investigating. Water reaching a socket or the machine's own electrics is a genuine shock and fire risk. If water has run under a fitted kitchen or through a ceiling, deal with the electrics first: if in any doubt, switch off the circuit at the consumer unit and call an electrician.

What you'll need

A torch
Old towels and a shallow tray
A screwdriver for the hose clips (optional)
A spirit level (optional)

Where a dishwasher leaks, and what each location means

Step by step

Turn it off at the socket and close the isolating valve.The isolating valve is usually a small lever or screw valve on the cold supply under the sink. Turn it a quarter turn so the lever lies across the pipe. Do this before pulling anything out.
Establish where the water appears and when.Front of the door, under the front, under the back, or only inside the cabinet next door. And when: on fill, during the wash, on drain, or all the time even when the machine is idle. Constant leaking while idle means the supply side, before the machine's own valve.
Check the door seal and the door alignment first.Run a finger round the gasket looking for a tear, a hardened flat spot or food debris sitting in it. Clean it with hot soapy water. A gasket that has gone hard and shiny at the bottom corners is a common failure and is a replaceable part on most machines.
Check the machine is level and sitting square.A machine leaning forward pushes water past the bottom of the door seal. A spirit level across the top and front to back, and adjust the feet. This is a very common cause after a machine has been moved or a floor has been relaid.
Rule out an overfill and excess foam.Water pouring over the bottom of the door during the wash, with visible foam, means washing-up liquid or hand soap has got into the machine. Nothing else foams like it. It takes several rinse cycles to clear, and it is a use error rather than a fault.
Look behind the machine at both hose connections.Pull the machine out slowly on towels. Check the inlet hose union at the isolating valve and at the machine, and the drain hose clip at the waste spigot. Feel the connections with a dry tissue rather than looking — a slow weep is invisible and obvious to paper.
Check the inlet hose along its whole length.Braided hoses fail from the inside and show a damp patch or a bulge before they burst. A hose that is more than about ten years old and shows any corrosion at the crimped ends should be replaced, and they are inexpensive.
Check the base tray for standing water.Tip a little water in the base tray and many machines will lock out with an error, which is the float switch doing its job. If the machine is showing a leak error with no visible water, water has already reached that tray from somewhere above.
Check the spray arm bearings and the tub seams if the leak is internal.A cracked spray arm, a broken arm retaining nut or a split at a tub seam sends water where it should not go. A rust stain on the outside of the tub or on the base tray points at the tub itself.
Stop and call an engineer for pump, door hinge and tub faults.A leaking circulation pump seal, a failed door hinge spring or a split tub are all internal jobs behind panels. On an integrated machine, they also need the machine unbolted from the cabinet. Keep it switched off and isolated until it is looked at.

Common mistakes

Mopping up and running it again to see if it happens — It will, and the second run adds to water already under a cabinet or through a ceiling. Isolate it, find the source, then test deliberately with towels down.
Overtightening the inlet hose union to stop a weep — The joint seals on a rubber washer inside the nut, and hand tight is correct. A spanner crushes the washer and turns a weep into a leak.

If it doesn't work

Water leaks even when the machine is off and has not run

Cause: The supply side is leaking upstream of the machine's own inlet valve — Fix: Close the isolating valve immediately. It is the hose, the union or the valve itself, and none of it needs the machine to be running.

Foam pouring out of the door

Cause: Washing-up liquid or hand soap in the machine — Fix: Run rinse-only cycles until the foam stops, adding a tablespoon of vegetable oil or salt to the sump to break it. Never use washing-up liquid in a dishwasher.

Machine stops with a leak or AquaStop error and will not restart

Cause: Float switch in the base tray has tripped — Fix: The tray has water in it. Find the source before resetting it — the lockout is protecting the floor, not misbehaving.

Water appears in the cupboard next to the machine, not under it

Cause: The drain hose connection at the sink waste, or the sink trap itself — Fix: Check the spigot clip and the trap joints. This is plumbing under the sink rather than an appliance fault.

Damp patch under an integrated machine noticed only by warped kickboard

Cause: A slow weep that has been running for weeks — Fix: Pull the machine out fully and dry the floor before finding the source. Slow leaks under integrated units cause more damage than fast ones because nobody sees them.

Questions people ask

How urgent is a small drip?

Urgent if it is under a fitted kitchen. Chipboard carcasses and floor decking absorb water and swell irreversibly, and the damage is usually worse than the appliance fault causing it. Isolate it and stop using the machine until it is fixed.

My machine has AquaStop — does that mean it cannot leak?

No. AquaStop-type systems protect against a burst inlet hose and against water collecting in the base tray. They do nothing about a failed door seal, a cracked tub or a drain hose that has come off at the sink end.