The short answer
Most dishwasher leaks are the door seal or a connection behind the machine. Turn the isolating valve off, dry everything, put paper down, and run one cycle watching - the stage the water appears at is most of the diagnosis.
What you actually see and hear
- Water at the front along the floor during the wash — The door seal, or something in the racks holding the door ajar.
- Water at the back only during drain — The drain hose connection.
- A damp plinth with no obvious source — A supply weep under constant pressure.
- Foam on the floor — Detergent rather than a fault.
- NEAR MISS - water running off the door when you open it at the end — Condensation. Normal on a hot cycle.
Causes, most likely first on this machine
- Door seal, alignment or a trapped item — First. The seal runs the whole way round a light door, and a handle proud of the top rack is enough to hold it fractionally open.
- Drain hose connection at the waste — Second. It is clamped behind the machine and disturbed whenever anything is done under the sink.
- Supply hose fitting or isolating valve — Third, and the one that soaks a plinth quietly because it weeps under mains pressure all day.
- Detergent overdose or the wrong product — Fourth, and always worth ruling out first because it costs nothing: suds climb past a sound seal.
- Tub seam or sump gasket on a plastic tub — Fifth. Plastic tubs flex with heat, and a seam that has been stressed can weep.
- Spray arm feed or internal hose — Last, and it needs the machine out of the cabinet.
Check in this order, and why
- Turn the isolating valve off first — The leak is under pressure until you do.
- Dry everything and lay kitchen paper front and back — Paper finds the first drop and where it came from.
- Run one cycle and note when water appears — Fill, wash and drain implicate different causes.
- Run a finger round the whole door seal — Looking for grit, tears and flattened sections.
What an owner can safely check
- Turn the water off at the isolating valve and dry the area — Do this before any diagnosis.
Tools: towelsAbout 10 min
- Clean the door seal and the edge it closes against — Grit in the seal is the single commonest cause.
Tools: clothAbout 15 min
- Check nothing in the racks holds the door fractionally open — A tall handle in the top rack is enough.
About 5 min
- Pull the machine forward and check every connection with a tissue — A tissue finds a weep a hand will miss.
Tools: tissue, towelAbout 25 min
- Use the correct detergent at the recommended dose for one cycle — If the leak stops, it was foam.
About 90 min
- STOP HERE before opening the sump or attempting to reseal a tub — That needs the machine out and the supply isolated.
Before you open anything
Safety
Unplug the appliance or switch off its breaker before removing any panel - a capacitor can hold a charge after the power is off. A dishwasher sits in a wet cabinet with a live connection behind it, so switch off at the breaker before pulling it out and close the isolating valve under the sink before touching any hose. A plastic tub holds heat, so let a hot cycle cool before reaching inside.
When to call a technician
Call when the seal is clean and intact, the connections are dry and water still reaches the floor - that points at the sump, a spray feed or the tub, and on a plastic tub a seam leak is often a replacement rather than a repair. Call urgently if water has been reaching a plinth or a floor void for any length of time, because that damage outruns the appliance. Keep the isolating valve closed until the source is known.
Nearest pages of this class
What this page does not cover
This page is written for the plastic-tub built-in dishwasher class, not for one family or model line. Where a brand- or model-specific page exists for your unit it is the more specific answer and it is linked above, so go there first if your machine is named. What is deliberately not here: spray arm and pump part numbers, heater ratings, door spring tensions and control diagnostics, all of which differ by family and belong on the page for that family.
Lead Appliance Repair Technician · 12 years experience
Experienced technician with 12 years specializing in washing machine and dryer repairs across all major brands.
