Dishwasher Not Draining? 5 Things to Check Before You Call a Technician

Water Standing in the Bottom of Your Dishwasher

You open the dishwasher expecting clean dishes and find an inch of murky water sitting in the bottom. It’s one of the most common calls we get here in Mission Viejo — and sometimes the fix is simpler than you’d think. Before you call us, here are five things worth checking.

1. The Garbage Disposal Knockout Plug

If you recently had a new garbage disposal installed, there’s a plastic knockout plug inside the dishwasher drain port on the disposal. If the installer forgot to remove it, your dishwasher has nowhere to drain. This sounds unusual, but we see it at least twice a month.

How to check: Look at where the dishwasher drain hose connects to the disposal. If the disposal is new, the plug may still be in place. A plumber or handyman can knock it out in minutes.

2. The Drain Filter

Most dishwashers made after 2010 have a manual filter at the bottom of the tub, near the spray arm base. If you’ve never cleaned it (and most people haven’t), it may be packed with food debris, grease, and calcium buildup — especially in South Orange County, where water hardness varies by neighborhood.

How to clean: Twist the cylindrical filter counterclockwise, pull it out, rinse under the faucet with a soft brush, and replace. Run an empty cycle afterward with a cup of white vinegar on the top rack.

3. The Drain Hose

The drain hose runs from the dishwasher to the garbage disposal or sink drain. If it’s kinked, pinched by the dishwasher being pushed too far back, or clogged with debris, water can’t exit.

How to check: Pull the dishwasher out slightly and inspect the hose for kinks. If it’s a corrugated hose, debris can accumulate in the ridges over time.

4. The Air Gap (If You Have One)

If you have a chrome or stainless cap on your countertop next to the faucet, that’s an air gap — a backflow prevention device required by code in many areas. If the air gap is clogged, the dishwasher can’t drain properly.

How to clean: Remove the chrome cap and the inner cap. Clean any debris. If water is backing up through the air gap, the line between the air gap and disposal is the problem.

5. The Drain Pump

If you’ve checked everything above and still have standing water, the drain pump itself may have failed. Listen during the drain cycle — if you hear humming but no water movement, the pump motor may be running but the impeller is jammed or broken. If you hear nothing at all, the pump motor may be dead or the control board isn’t sending power to it.

This is where a professional comes in. Drain pump replacement involves disassembling the lower portion of the dishwasher and electrical work. Typical cost for a drain pump replacement in the Mission Viejo area is $200–$375 depending on the brand.

When to Skip the DIY and Call Us

• Water is backing up into the sink when the dishwasher runs
• You smell burning or hear grinding sounds
• Error codes appear on the display (Bosch E24/E25, Samsung 5E, LG OE)
• The dishwasher won’t start at all (electrical issue, not just drainage)

Call Mission Viejo Appliance Repair at (949) 954-5358. We diagnose the problem for $89, waived when you proceed with the repair.