Open the dishwasher after the cycle and there is a pool of grey water sitting in the bottom. It is one of the most common dishwasher complaints, and in most cases the cause is in the drain path rather than the dishwasher itself.
Here is how a dishwasher drains, what blocks it, and the order we check things in.
First, is it actually a problem?
A small amount of clean water in the sump at the bottom of the tub is normal. It keeps the pump seal wet. Standing water that covers the bottom of the tub, smells, or has food in it is not normal and will not clear itself.
Check the filter and sump
Most modern dishwashers have a removable cylindrical filter at the bottom of the tub. Twist it out, rinse it under the tap and clear any debris from the sump underneath. Glass, labels, seeds and bones collect here. Run a rinse cycle. If the water clears, you are done, and cleaning the filter monthly will keep it that way.
Check the drain hose and the air gap
The drain hose runs from the dishwasher to the sink drain or garbage disposal, often through an air gap (the small chrome cylinder next to the faucet). Kinks behind the dishwasher, a hose that has sagged into a low loop, or a clogged air gap all stop drainage. Pop the cap off the air gap and clear any debris.
The garbage disposal knockout plug
If the dishwasher stopped draining right after a new garbage disposal was installed, the knockout plug inside the disposal’s dishwasher inlet was almost certainly never removed. The dishwasher pumps against a solid wall. Removing the plug fixes it in minutes, and it is one of the most common causes we see in Springfield homes after a kitchen update.
Inside the dishwasher
- Failed drain pump. The pump hums at the end of the cycle but moves nothing, or is silent. The impeller may be jammed with a shard of glass or the motor may have failed.
- Stuck check valve. The one-way flap in the drain line jams and water flows back into the tub after draining.
- Control fault. The dishwasher never runs the drain portion of the cycle. Less common, but it happens after power interruptions.
- Error codes. Bosch E24 and E25, Samsung 5C, LG OE and similar codes all mean the dishwasher has detected a drain problem. They point to the system, not the exact part.
When to call a technician
Call when the filter is clean, the hose and air gap are clear and the dishwasher still will not drain, or when you hear the pump hum without moving water. Do not keep running cycles: repeated attempts against a blockage can overheat the drain pump. A drain pump is a routine repair on a dishwasher under about ten years old.
Frequently asked questions
Quick answers to the questions we hear most about this problem.
How do I get the standing water out?
Scoop or sponge most of it out, then remove and clean the filter. If it still will not drain on a rinse cycle, leave the rest for the technician.
Why does my dishwasher smell?
Food trapped in the filter, sump or drain hose, usually combined with slow drainage. Cleaning the filter and running a hot cycle with a dishwasher cleaner helps; persistent smell with standing water means a drain problem.
Is it cheaper to fix or replace a dishwasher that won’t drain?
Almost always fix. Filters, hoses, valves and drain pumps are modest repairs. Our $75 diagnostic fee covers the inspection and diagnosis and is applied toward the approved repair.
Related services
Need a hand with it? Alliance Appliance Services diagnoses first and explains the repair before any work starts. Call (571) 303-8548 or request a repair online. We serve Springfield, Alexandria, Fairfax, Arlington and the surrounding Northern Virginia communities.