Quick answer
A dishwasher with standing water at the bottom has one of four causes: the drain hose is kinked or clogged, the garbage disposal drain knockout wasn't removed during install, the air gap on the countertop is clogged, or the dishwasher's own filter is blocked. Check the filter first (60 seconds), then the disposal knockout (common on new install), then the drain hose. Under $10 in parts if anything at all.
Key facts
| Common causes | Clogged internal filter; Garbage disposal knockout not removed; Clogged air gap; Kinked or clogged drain hose |
|---|---|
| DIY difficulty | Easy |
| Time to fix | 30 min |
| Parts cost | $0–$10 parts |
| Tools needed | Screwdriver, pliers, towels |
| When to call a pro | If drain pump is failing (loud grinding, no drain sound) |
What's happening
A dishwasher drains through a hose that connects to either the garbage disposal or the sink drain, often through an air gap fitting on the countertop. When the drain pump runs, water is pushed through this path. Any blockage stops drainage. New installs commonly fail because the plug inside the garbage disposal drain (called the 'knockout') wasn't removed. Older dishwashers accumulate food debris in the internal filter and pump housing.
Common causes (ranked by frequency)
- Clogged internal filter 35% of cases
Every modern dishwasher has a filter at the bottom (under the lower spray arm). Food debris accumulates. Pull the filter, rinse, reinstall.
- Garbage disposal knockout not removed 25%
New installs fail this way. The disposal comes with a knockout plug in the dishwasher inlet — it must be removed before connecting. If it wasn't, water has nowhere to go.
- Clogged air gap 20%
The small chrome cylinder on the countertop next to the faucet. Food buildup inside. Pop the cap, clean.
- Kinked or clogged drain hose 15%
The hose runs under the sink from dishwasher to disposal or sink drain. Kinks stop flow. Debris can also lodge inside.
- Failed drain pump 5%
Symptom: no drain sound at all when the drain cycle runs. Replacement is $50–$120 part but requires pulling the dishwasher out — moderate DIY or call a pro.
How to diagnose
- Note the sound during drain cycle. Normal drain: a distinct pumping sound for 30–60 seconds. Silent = pump failed. Grinding = pump failing.
- Check the internal filter first. Pull the bottom rack, twist the filter counterclockwise, lift out. Rinse under hot water.
- If this is a new dishwasher install: Check the disposal knockout. See fix #2.
- Check the air gap. If present (chrome dome on countertop), pop the cap and look for buildup.
The fixes
Fix #1 — Clean the filter 60-second fix
The most common cause and easiest fix. Do this monthly as maintenance.
Tools
- Nothing — just your hands
Materials
- Pull out the lower rack.
- Locate the filter — usually a cylindrical piece near the center at the bottom, under the spray arm.
- Twist counterclockwise 1/4 turn and lift out.
- Rinse under hot water, scrubbing with a soft brush if needed.
- Reinstall — align with slots, twist clockwise until locked.
- Run a short cycle to test.
Fix #2 — Remove the disposal knockout
For new dishwasher installs where drainage never worked. The knockout plug must be removed from the garbage disposal's dishwasher inlet.
Tools
- Hammer
- Screwdriver (flathead)
- Pliers
- Flashlight
- Bucket
Materials
- Turn off power to the disposal at the wall switch AND unplug it or trip its breaker.
- Disconnect the dishwasher drain hose from the disposal inlet — small hose clamp near the top of the disposal.
- Look inside the inlet. You'll see a plastic plug (the knockout).
- Insert screwdriver into the plug and tap firmly with hammer — the knockout falls into the disposal chamber.
- Reach in with pliers (power still off!) and retrieve the plug. Do NOT leave it — it'll grind and damage the disposal.
- Reconnect the dishwasher drain hose.
- Restore power to disposal.
Fix #3 — Clean the air gap
The chrome cylinder on the counter near the faucet. Small food particles accumulate inside.
Tools
- Nothing — just hands
Materials
- Pop off the chrome cap — usually pulls straight up.
- Lift the plastic cover underneath.
- Inspect for debris. Clean with a bottle brush or your finger.
- Reassemble.
Prevention
Clean the internal filter monthly. Scrape (don't rinse) plates before loading — modern dishwashers handle stuck-on food, but bones, seeds, and stickers cause repeat clogs. Run the disposal briefly before starting the dishwasher if they share drainage. Once a month, run an empty cycle with a cup of white vinegar on the top rack — cleans internal water pathways.
When to call a pro
When to stop and call a pro
- You've checked filter, disposal knockout, air gap, and hose — dishwasher still won't drain.
- Grinding or unusual noise during drain cycle — drain pump is failing.
- Dishwasher is more than 10 years old and this is one of multiple recent issues — replacement is often more cost-effective.
- Water leaking from underneath the dishwasher — separate issue, could be a supply line or pump seal.
Appliance repair service call: $100–$200. Drain pump replacement: $150–$350 including labor. Full dishwasher replacement: $700–$1,500.
Cost estimate
Cost estimate
Frequently asked questions
The water at the bottom after a completed cycle is technically dirty — food particles that couldn't drain. Not dangerous but unpleasant. Fix the drain issue rather than manually bailing water out.
Never. Chemical drain cleaners damage dishwasher seals, gaskets, and food-contact surfaces. Also they don't work on the typical dishwasher clog (mechanical, not organic buildup).
Monthly for typical households. Weekly if you don't scrape plates. Signs the filter needs attention: standing water, film on glassware, or a soured smell.
The drain hose is either not looped high (should form a high loop under the sink) or the disposal/sink drain is clogged. Air gaps prevent this too — but require additional installation.