Dishwasher Not Draining — Causes and What to Check
Quick Answer
A dishwasher with standing water after a cycle most commonly has a clogged filter or sump, food debris in the drain path, a kinked or clogged drain hose, a blocked air gap, or — on new installations next to a garbage disposal — a knockout plug that was never removed. Check these in order with the power off at the breaker before calling a technician.
Common symptoms
| Symptom | Possible cause | Safe next check | When to call a pro |
|---|---|---|---|
| Standing water covering the tub bottom after cycle | Clogged filter or sump debris | Remove and rinse the filter assembly under running water; clear visible debris from sump | If filter is clean and water remains after a test cycle |
| Water drains slowly but not completely | Partial drain hose clog or kinked hose | Pull dishwasher out slightly and inspect hose behind the unit for kinks; check connection at disposal or drain | If hose requires disconnection and you are not comfortable with the repair |
| Dishwasher overflows or backs up into sink | Air gap blockage or high-loop drain issue | Inspect the air gap fitting on the counter (twist off cap, clear debris); confirm drain hose has a high loop | If the air gap is clear but backup continues |
| New dishwasher never drained after installation | Garbage disposal knockout plug left in place | With power off, inspect the disposal inlet; use a screwdriver and hammer to knock out the plug | If uncomfortable working near the disposal |
| Drain cycle runs but no water movement | Failed drain pump or blocked pump impeller | Listen for the drain pump humming during the drain cycle; clear visible debris from the sump area | Pump replacement requires disassembly — call a technician |
Most common causes
Standing water in the bottom of a dishwasher at the end of a cycle almost always traces back to a blocked drain path. The fix is often simpler than it looks.
- Clogged filter or sump debris (most common). Modern dishwashers rely on a user-cleanable filter at the tub bottom rather than a self-cleaning grinder. Food particles, labels, and debris build up over time and restrict drainage. This is the first thing to check.
- Food debris in the drain path. Even with a clean filter, large food scraps can accumulate in the sump area directly below the filter and block the drain opening.
- Kinked or clogged drain hose. The drain hose runs from the pump under the tub to the drain connection under the sink. A sharp bend, a kink caused by moving the appliance, or an internal clog can stop water flow entirely.
- Blocked air gap. If your installation includes an air gap fitting on the countertop, it can clog with debris and prevent proper drainage.
- Garbage disposal knockout plug. This affects new dishwasher installations only. When a dishwasher is connected to a new garbage disposal, a knockout plug inside the disposal's dishwasher inlet must be removed. If it was overlooked during installation, the dishwasher has never had a clear drain path.
- Failed drain pump. The pump that forces water out can fail mechanically or have a blocked impeller. This is less common than blockages but does require a technician to repair.
Safe troubleshooting steps
Turn off the dishwasher and disconnect power at the breaker before reaching into the tub or pulling the unit away from the wall. Water and electricity don't mix.
- Remove and clean the filter. Open the dishwasher and locate the cylindrical filter at the bottom center of the tub. Twist counterclockwise to release it, lift out the flat mesh screen beneath, and rinse both under warm water. Clear any food from the sump opening below.
- Run a rinse-only cycle. After cleaning the filter, run a short rinse cycle and watch whether it drains. This rules in or out a simple filter clog.
- Inspect the air gap (if present). The air gap is the small fitting near your faucet on the countertop. Twist or pop off the decorative cap and the interior cover, and clear any debris with a small brush or cloth.
- Check the garbage disposal. Run the disposal with water flowing and confirm it drains completely. If you recently installed the dishwasher with a new disposal, check whether the knockout plug was removed from the disposal's dishwasher inlet.
- Inspect the drain hose. With power off, pull the dishwasher out slightly and trace the drain hose from the pump to its connection under the sink. Look for kinks, tight bends, or a connection that has slipped off. A high loop in the hose (secured near the underside of the countertop) is needed if no air gap is present.
- Listen during the drain cycle. If you hear the pump humming but no water moves, the impeller may be blocked or the pump is failing.
When to call a professional
Contact a qualified appliance technician if:
- The filter is clean, the hose is clear, and water still doesn't drain.
- You hear the pump cycle but nothing drains, pointing to a pump or valve failure.
- The drain hose needs replacement and you are not comfortable disconnecting plumbing under the sink.
- There is any sign of water under the floor or behind the unit.
Repair or replace?
A drain pump repair is one of the more cost-effective dishwasher fixes. But if the unit is old, consider the full picture. Our repair-or-replace guide covers how to think through the decision, and the Repair vs. Replace calculator can help you frame the numbers. For context on what technicians typically charge, see the appliance repair cost guide.
How to prevent it
- Clean the filter monthly or more often if you run the dishwasher daily.
- Scrape large food pieces off dishes before loading — you don't need to pre-rinse, but chunks of food and labels can block the filter quickly.
- Run the garbage disposal before starting the dishwasher to clear the shared drain line.
- Run hot water at the sink for 30 seconds before starting the dishwasher to prime the drain line with warm water.
Estimated costs
| Item | Typical range (USD) | As of | Scope / source |
|---|---|---|---|
| Drain pump replacement (parts + labor)† | $150–$350 | 2026 | United States · HomeFixHelper illustrative range — Verify with local quotes |
| Drain hose replacement (parts + labor)† | $80–$200 | 2026 | United States · HomeFixHelper illustrative range — Verify with local quotes |
† Illustrative placeholder pending verified source data. Do not treat as a quote.
Costs vary by region, brand, and the specific failure. Always get written quotes from licensed local professionals.
Frequently asked questions
Why is there always a little water at the bottom of my dishwasher?
A small amount of water — typically less than an inch — at the very bottom of the tub is normal on most dishwashers. It keeps the pump seal from drying out. If water covers the filter or fills more than an inch or two, there is a drainage problem worth investigating.
How do I clean my dishwasher filter?
Most modern dishwashers have a two-part removable filter at the bottom of the tub. Twist out the cylindrical upper filter and lift out the flat mesh screen. Rinse both under warm running water and use a soft brush to remove any food buildup. Replace both pieces and confirm they are locked back into position. Cleaning frequency varies by use — monthly is a reasonable target for typical households.
Can a clogged garbage disposal cause my dishwasher not to drain?
Yes. Most dishwashers drain into the garbage disposal or the drain line nearby. If the disposal is backed up or its inlet is blocked, dishwasher water has nowhere to go. Run the disposal and flush it with water before running the dishwasher, and confirm it is draining freely.
What is a dishwasher air gap and does mine have one?
An air gap is a fitting — usually a small chrome dome on the countertop near the faucet — that prevents dirty water from siphoning back into the dishwasher. Not all installations include one; some use a high-loop drain hose instead. If you have an air gap, debris can accumulate inside the cap and block drainage. Remove the decorative cover, clean out any debris, and reinstall.
Should I try to replace the drain pump myself?
Drain pump replacement requires removing the dishwasher's lower spray arm, filter assembly, and often the tub floor panel to access the pump. It is a manageable repair for someone comfortable with appliance disassembly, but mistakes can create leaks. If you are unsure, a technician visit is the safer choice. Weigh the repair cost against the unit's age using our [repair-or-replace guide](/appliances/repair-or-replace-appliance).
Sources
- Water Efficiency — Dishwashers — U.S. Department of Energy (link). Checked October 15, 2026. Supports: Context on dishwasher water use and efficient operation.
- Dishwasher owner's manual (your model) — Manufacturer documentation. Checked October 15, 2026. Supports: Model-specific filter location, cleaning procedure, and drain path.