A small puddle under the dishwasher is easy to dismiss as a one-off. It usually isn't. Left alone, water works its way into floorboards, swells cabinetry from the inside, and creates mould in the grout around the base. The longer it keeps leaking, the more expensive the fix becomes -- and that's before you've touched the dishwasher itself.
The good news is that the source of the leak usually isn't hard to find. Where the water appears tells you a lot before you've even opened anything up. For repairs across Sydney, Melbourne, Brisbane, Perth, and Adelaide, National Appliance Repairs offers same-day call-outs with a 12-month warranty on all parts.
Finding the Source
Get down with a torch while the machine is running -- or just after it finishes draining -- and watch carefully. Water that "comes from under the dishwasher" often turns out to be running down the inside of the door, spreading along the floor tiles, and pooling near the machine's base. That's a door seal problem, not an internal one. The two have different fixes.
- Water tracking along the front edge of the door -- door seal or door alignment
- Water pooling directly underneath the machine -- pump seal, sump gasket, or drain hose
- Water appearing near the connection at the back -- inlet hose fitting
- Water during the fill phase rather than the drain -- float switch or inlet valve
Door Seal (Gasket)
The most common cause, by a clear margin. The rubber or silicone seal around the door perimeter keeps water inside the tub during a wash cycle. Over time it flattens, cracks, or collects debris at the base that breaks the seal. Water then escapes during the wash cycle, runs down the door face, and spreads across the floor -- making it look like a bottom leak.
Run your finger around the full length of the gasket and check for:
- Visible cracks or tears
- Sections that have pulled away from their channel
- Food debris or dried detergent built up in the bottom corners (this is where most gasket leaks actually start)
- Flat spots where the rubber has lost its original shape
Cleaning the gasket with warm soapy water often fixes debris-related leaks immediately. A damaged or permanently deformed gasket needs replacing. Replacement gaskets for most brands cost $40--$80 and press into the door channel without special tools.
Door Alignment and Machine Level
A door that doesn't close square will press the gasket unevenly, creating a gap even when the gasket itself is undamaged. This happens when the machine gets knocked, when it wasn't properly secured to the cabinetry during installation, or simply when the levelling legs have worked loose.
Place a spirit level on top of the machine and check it both front-to-back and side-to-side. An unlevel machine allows water to overflow at one side of the tub during the wash cycle, which exits under the door. Adjust the levelling legs -- usually accessible from the front under the kickplate -- until the bubble centres in both directions. Also check the door closes with a firm, even click.
Pump Seal and Sump Gasket
If the water is genuinely coming from underneath rather than tracking from the door, the pump or sump is the next place to look. The sump collects water at the base of the tub before the pump clears it. The seal around the sump, and the seal where the pump attaches to it, both wear with age and heavy use.
This leak typically only becomes visible if you remove the kickplate and look underneath with a torch while the machine runs a full cycle. You won't see it from above.
Accessing and replacing a pump seal requires partially disassembling the pump assembly. Putting it back together incorrectly causes more leaks or damages the pump motor. This one needs a technician.
Drain Hose
The drain hose carries water from the pump to the sink drain or waste outlet. It can develop a split, a clamp can work loose, or (very commonly) it ends up in the wrong position: either compressed against the back of the cabinet, or with the outlet end sitting submerged in water under the sink. Both cause leaks or backflow.
While a cycle is running, pull the machine out slightly and look at the drain hose:
- Any water dripping from the hose body or at either connection point
- Whether the hose end sits submerged in standing water under the sink
- Whether the hose has a proper elevated loop before dropping to the drain connection -- it should rise close to bench height before going down
A cracked hose can usually be replaced as a DIY job. Incorrect routing causing backflow just needs the hose repositioned.
Float Switch
Inside the tub, near the front, is a small float dome. It rises with the water level and triggers a switch that tells the inlet valve to stop filling. If the float jams down -- food debris is almost always the cause -- the valve stays open and the machine overfills. Water spills over the tub edge and exits under the door.
Press the float up and down. It should move freely without resistance. If it's stuck, clear the debris and test again. If the microswitch beneath it has failed, the switch itself needs replacing.
Too Much Detergent
Excess detergent creates foam that the machine reads as water volume. The suds build up until they're forced out under the door. If the leak is consistent and you notice foam in the tub or at the base of the door, reduce the detergent quantity. In soft-water areas, the recommended amount on the packaging is usually too much -- try using significantly less and see whether the foam disappears.
Causes at a Glance
| Where the Water Appears | Most Likely Cause |
|---|---|
| Tracks along front of door during wash | Door seal dirty, worn, or door misaligned |
| Directly underneath machine | Pump seal, sump gasket, or drain hose |
| At base during fill phase | Float stuck down, or inlet valve fault |
| Rear of machine | Inlet hose fitting loose or cracked |
| Foam visible alongside leak | Too much detergent |
FAQ
Can I keep using the dishwasher while it's leaking?
It's not a good idea. Every cycle adds more water to the floor and cabinetry. A minor leak can become a floor replacement job in a few weeks.
Can I replace a door gasket myself?
Usually, yes. Most gaskets press into a channel and don't need tools. Order the correct part for your model, warm the new gasket with a hairdryer on low heat to make it pliable, and press it in firmly starting at the top centre.
Why does my dishwasher only leak sometimes?
Intermittent leaks often point to an overfill issue (float switch or inlet valve), foam from excess detergent, or a door seal that only fails at certain water pressures or during particular wash phases.
How do I check if the dishwasher is level?
Set a spirit level on top and check it both front-to-back and side-to-side. Adjust the levelling legs under the kickplate until it sits flat in both directions.
What's the difference between a pump seal leak and a door seal leak?
A door seal leak tracks down the door face and spreads across the floor. A pump seal leak appears directly underneath the machine and is only visible with the kickplate removed. They look similar from across the kitchen but have completely different fixes.
Conclusion
Most dishwasher leaks start at the door seal. Clean it first, check for damage, and confirm the machine sits level. If the water is coming from underneath rather than the door, the pump seal or drain hose needs a proper look -- and that work is better handled by a technician to avoid making things worse. National Appliance Repairs diagnoses and fixes dishwasher leaks across all major brands, with same-day availability in Australia's major cities. Call 1300 434 380 to book.
