Short answer
To clean a dishwasher drain, switch off the power first, then check in this order: the filter in the bottom of the tub, the drain hose for kinks, the high loop or air gap, and the garbage disposal, including the knockout plug on a new disposal. If water still stands after those checks, call an appliance technician or plumber.
Dishwasher standing water after a cycle is a common problem, and the cause is often a small blockage you can reach. This guide gives an ordered check list for a dishwasher not draining: what to look at, what each part does in general terms, and when to stop. Appliance designs differ, so your owner's manual comes first for filter removal and any model-specific steps.
The technical points below come from an independent appliance repair guide (iFixit's Dishwasher Not Draining guide) and a home-repair article (Hunker), both opened for this page. They are not from a manufacturer, an extension service or a government agency, so treat this as general guidance and check your manual.
Safety first: power off
- Switch off the power. The repair guide suggests disconnecting the electrical supply and turning off the water before working on hoses or electrical parts. For a plug-in unit, unplug it. For a hard-wired unit, turn off the breaker. Hunker also says to unplug before inspecting the drain.
- Remove standing water first. The guide says to remove water in the bottom of the machine with a sponge and bucket.
- Skip chemical drain cleaners. They are not part of the steps below. If you are thinking of one, ask an appliance technician or plumber first, and never mix cleaning products. Ohio State University Extension warns that a caustic drain cleaner followed by bleach can release chlorine gas.
- Wear gloves and keep towels and a bucket nearby.
Why a dishwasher stops draining: common causes
| Part | What it does | Typical problem |
|---|---|---|
| Filter or drain basket | Catches food at the bottom of the tub so it does not reach the pump and drain | Clogged with food debris |
| Drain hose | Carries water from the dishwasher to the sink drain or disposal | Kinked, pinched or clogged |
| High loop or air gap | Part of the hose, or a fitting by the sink, that keeps sink water from running back into the dishwasher | Blocked air gap, or a loop that has slipped down |
| Garbage disposal and its knockout plug | Often shares the dishwasher drain | Disposal clogged, or the knockout plug on a new disposal not removed |
| Drain pump | Pushes water out | Blocked impeller or a worn pump |
The repair guide says that taking longer to remove water, or leaving standing water, is a sign of a bad pump, but that is the last thing to suspect, not the first.
How to clean a dishwasher drain: an ordered check list
- Power off and remove the water, as above.
- Clean the filter. Remove the bottom rack. The repair guide says to remove the coarse and fine filters, clean them and twist them back into place. Hunker adds that you scrub the mesh with dish soap and an old toothbrush, rinse it, and that some basket filters are held by screws. Do not force a part; use your manual.
- Look at the drain opening. Use a flashlight and scoop out loose debris from the mouth of the drain with a cloth.
- Check the drain hose. The guide says to make sure it is not pinched or kinked and to replace it if needed. Hunker suggests that, if the sink drains normally, you can look at where the hose meets the main drain, and remove the pipe at both ends to check it for clogs. Have a bucket ready.
- Check the high loop or air gap. The guide says the hose should go to an air gap, check valve or high loop under the sink, and that you should check that these are clear. If you have an air gap fitting on the counter, lift off its cover and clear any debris.
- Check the disposal. The guide says to run the disposal, since it often shares the dishwasher drain, then flush with cold water for 20 seconds to clear debris.
- On a new disposal, check the knockout plug. The guide says to confirm the knockout plug is removed from the drain tube, because if it is not, the dishwasher cannot drain properly. If you are not sure how, ask the person who installed it, or a plumber.
- Test. Reassemble, then run a short cycle and look for leaks at every joint you touched.
This order starts with the parts you can clean without taking anything apart and ends with the ones that need tools. Stop at any step where you are unsure.
The high loop and air gap in plain terms
A dishwasher shares a drain with the kitchen sink or garbage disposal, so something must stop sink water from running backward into the machine. Two common ways are a high loop, where the drain hose is held up high under the counter before it connects, and an air gap, a small fitting on the sink or counter. The repair guide mentions all three options (air gap, check valve and high loop) under the sink.
Which one your home uses, and what the plumbing code asks for, varies by manufacturer and by place. Check your dishwasher's installation instructions and ask your local building or plumbing department what applies. If water leaks out of an air gap during a cycle, stop and have a plumber or appliance technician look at it.
Disposal knockout plug on a new disposal
A new garbage disposal may arrive with a plug blocking the dishwasher inlet. The repair guide says the dishwasher cannot drain properly if it is left in. If your dishwasher stopped draining after a new disposal was installed, this is the first thing to check. Turn off power to the disposal before anyone works on it. If you are not sure how to check or remove the plug, ask the installer or a plumber.
When to stop and call
- The check list above did not help. The repair guide says that if you have finished the checks without success, hire an appliance technician. Pump and control problems are theirs.
- The sink drains slowly too. The dishwasher may only be showing a clog in the kitchen drain line. Call a plumber and read clogged drain: DIY or call a plumber.
- Water backs up into the sink or comes out of the air gap repeatedly.
- Two or more fixtures are slow, or sewage smells or water appears in a basement drain. Stop using water and call a licensed plumber now. See drain cleaning near me.
- You see a leak, a damaged hose or electrical parts you do not want to touch.
Tell the technician what you checked and in what order. For what a drain visit may cost, see drain cleaning cost.
Prevent dishwasher drain problems
- Scrape food into the trash before loading, rather than leaving it for the filter to catch.
- Clean the filter regularly, following your manual.
- Keep grease out of the kitchen drain. If you have a septic tank, EPA advises never pouring cooking oil or grease down the drain and limiting the use of a garbage disposal.
- Run the disposal and flush the sink before a cycle if the two share a drain.
For septic homes, see what not to flush with a septic system.
What to look up where you live
- Your dishwasher and disposal manuals: for the filter location and the installation requirements.
- Local building or plumbing department: for whether an air gap or a high loop is required where you live.
- State or provincial plumbing licensing board: to check a plumber's license.
Rules differ by place. Check the current rules for your state or county. For Canadian readers: plumbing is regulated by each province, models and labels differ, and quotes are in Canadian dollars.
For plumbing and drain company owners
Dishwasher not draining is a search homeowners make before they decide whether the problem is the appliance or the plumbing. If you want to be found for the plumbing side, read plumbing SEO guide and plumber website design. You can also book a call with LiveLeadsLane. LiveLeadsLane is a marketing practice for contractors, not a directory, and it does not take jobs or refer homeowners.
