You open the dishwasher expecting clean dishes and instead find an inch of murky water pooled in the bottom. It’s one of the most common calls we get from homeowners around Tacoma and South King County, and the good news is that a fair number of these you can sort out yourself in about twenty minutes. Let’s walk through it the way I would if I were standing in your kitchen.
First, Make It Safe
Before you reach into anything, kill the power. Dishwashers mix water and electricity, and you don’t want both live while your hands are in the sump.
- Switch off the dishwasher’s circuit breaker, or unplug it if the cord is accessible under the sink.
- Sop up the standing water with a cup, a turkey baster, and towels until the basin is as dry as you can get it. You need a clear view of the bottom.
- Lay down a towel to catch drips when you pull hoses loose later.
If you have a Bosch, Whirlpool, or similar model flashing an error like E15, E24, or a blinking drain light, don’t panic. Those codes almost always mean the machine sensed water it couldn’t pump out, which is exactly what we’re about to chase down. The code is a symptom, not a diagnosis.
Step 1: Clear the Filter and Sump
This is the single most common culprit, especially here in Puget Sound where hard water leaves mineral scale and food debris builds up fast. At the bottom of the tub you’ll find a cylindrical filter assembly, usually a coarse mesh you can twist out by hand (typically a quarter turn counterclockwise).
- Pull the filter and rinse it under hot water. Use an old toothbrush on the fine mesh.
- Reach into the sump opening underneath and feel for debris: broken glass, a chunk of label, a fruit pit, a wad of grease.
- Check the small drain port and the impeller area if you can see it. Anything blocking that opening stops the pump cold.
Reinstall the filter snugly. A filter that isn’t seated all the way can trip an error on newer machines.
Step 2: Check the Drain Hose and Air Gap
If the sump is clean, follow the water’s path out. The drain hose runs from the dishwasher pump up under the sink to either the garbage disposal or an air gap, then to the drain.
The drain hose
Pull your dishwasher’s kickplate or look under the sink and trace the corrugated hose. It’s supposed to loop up high (the “high loop”) before heading down, which keeps dirty sink water from siphoning back. Look for:
- A kink where the hose bends sharply behind the unit.
- A sag full of standing gunk you can feel by squeezing along its length.
- A clog at either end. Disconnect it over a bucket and run water through to confirm it flows freely.
The air gap
That little chrome cylinder on the back of your sink or countertop is the air gap. Twist off the cap and the cover, and you’ll often find it packed with sludge. Clean it out and snap it back together. A blocked air gap will absolutely back water up into the tub.
Step 3: The Knockout Plug (the One Everyone Misses)
Here’s the gotcha that catches a lot of folks after a kitchen update. If you recently installed a new garbage disposal and the dishwasher hasn’t drained right since, this is very likely your problem.
Every new disposal ships with a solid knockout plug sealing the dishwasher inlet on its side. It has to be punched out before the dishwasher can drain into it. If the installer forgot, the dishwasher water has nowhere to go.
- Unplug the disposal first.
- Find the dishwasher inlet nub on the upper side of the disposal and disconnect the hose.
- Put a flathead screwdriver into the inlet and tap it with a hammer until the plug pops loose, then fish the plastic disc out of the disposal. Don’t leave it inside.
- Reconnect everything and test.
Step 4: Test the Drain Pump
If everything upstream is clear and water still sits, suspect the drain pump itself. With power restored, start a drain cycle and put your ear near the lower front of the machine.
- A healthy pump makes a steady whirring hum as water leaves.
- A loud buzz or grind with no water movement usually means the impeller is jammed or the pump motor is failing.
- Dead silence often points to a failed pump, a broken wire, or a control board that isn’t sending the signal.
Quick reality check: if you hear the pump strain and stop, power down again and re-inspect the sump. Glass shards love to wedge into impeller blades.
When It’s Time to Call
You’ve cleaned the filter, cleared the hose and air gap, knocked out the plug, and the pump still won’t move water, or it’s throwing that E15 or E24 code repeatedly. At that point you’re likely looking at a failed drain pump, a leak-sensor float that’s tripped, or a control board issue, and those need a meter and the right part to diagnose safely.
If you’d rather not chase it further, we’re glad to help. Our $79 diagnostic gets credited toward the repair, every job is backed by a 180-day parts and labor warranty, and same-day service is usually available across Tacoma and South King County. Book a repair online or call us at 253-386-7788, and we’ll get your dishwasher draining again.