Dishwasher Not Draining: the Checks Before You Call

You open the dishwasher after a cycle and there it is: an inch or two of dirty water sitting in the bottom, not going anywhere. The dishes are clean enough, the machine sounds like it ran, but the water stayed. A dishwasher that will not drain is one of the most common appliance complaints, and it is also one of the most fixable, because the cause is usually something simple and visible: a clogged filter, a blocked drain hose, a garbage disposal that was just installed, or a drain pump struggling with debris. Before you call anyone, there is a short list of checks worth working through, in order, because they solve the problem most of the time and they cost nothing.

One thing to know before you start: a little water in the bottom of a dishwasher is normal. Most machines keep a small amount in the sump to keep the seals wet. What is not normal is standing water that covers the filter, water that stays after you run a drain cycle, or water that comes back up into the sink when the dishwasher runs. Those are the signs of a real drainage problem, and this guide walks through it step by step, from the easy checks to the point where you should stop and call a pro.

The filter sits at the bottom of the tub, usually a cylindrical mesh piece you can twist out by hand, sometimes under a flat cover. Its job is to catch food particles before they reach the pump, and it does that job until it is so loaded with grease and debris that water cannot get through it at all. If you have never cleaned your dishwasher filter, or you cannot remember the last time you did, start here. It is the single most common cause of slow draining, and it is the easiest fix in the whole machine.

Pull the bottom rack out so you can reach the floor of the tub. Twist the filter counterclockwise and lift it out, along with any flat mesh screen underneath it. Rinse both under hot running water, and use a soft brush or an old toothbrush on the mesh to get the greasy film off. While the filter is out, look into the sump underneath it. You will often find the culprit sitting right there: a piece of glass, a popcorn kernel, a twist tie, a small bone, or a shard of a broken plate. Fish it out with tongs or your fingers, and wipe the sump clean.

Put the filter back the way it came out, making sure it locks into place. A filter that is not seated properly lets debris straight into the pump, which is how a small problem becomes a pump problem. Then run a short cycle or a rinse cycle and watch the bottom of the tub. If the water drains and the filter was dirty, you are done, and you have just learned a maintenance habit worth keeping: clean the filter every month or so, more often if you do not rinse dishes before loading them. A clean filter is the difference between a dishwasher that drains and one that slowly chokes. Washing machines choke the same way, and the checks for a washer that will not drain start in a similar place.

If your dishwasher drains through a garbage disposal, and especially if the disposal was recently installed or replaced, check the drain hose connection at the disposal. The dishwasher drain hose connects to a small inlet on the side of the disposal, and inside that inlet is a knockout plug, a small plastic disc that seals the inlet until a dishwasher is connected. When a disposal is installed, that plug is supposed to be knocked out. When it is not, the dishwasher has nowhere to drain, and the water backs up into the tub.

This is the classic cause of a brand-new dishwasher that has never drained properly, and it is also the classic cause of a dishwasher that stops draining the day a new disposal goes in. The fix takes a few minutes, but it involves working under the sink, so take your time. Turn off the disposal at the switch, and if you can, unplug it or switch it off at the breaker. Disconnect the drain hose from the disposal inlet, look inside the inlet, and see if the plug is still there. If it is, tap it out with a screwdriver and a light hammer, and fish the disc out of the disposal so it does not end up in the drain.

If the filter is clean and the disposal connection is fine, the next suspect is the drain hose. A dishwasher drain hose is a flexible tube, and it can kink where it passes through the cabinet wall, or it can clog with grease and food where it connects to the drain. A kink is easy to spot if you can see the hose run: look for a sharp bend, especially where the hose goes through a hole in the cabinet side, and straighten it out. A clog is harder to see, but you can sometimes feel it: run a drain cycle and feel along the hose for a section that stays cold while the rest warms up, which is where the water is not flowing.

If the filter is clean, the hose is clear, and the disposal connection is right, and the water still sits there, the drain pump is the next thing to consider. The pump sits at the bottom of the machine and pushes water out through the drain hose. When it fails, or when debris gets into it, you usually hear it: a humming or buzzing sound during the drain part of the cycle, with no water moving, or a grinding noise that was not there before.

There is a limited amount you can do here yourself. With the power off at the breaker, you can sometimes reach the pump from underneath the machine and check for debris in the impeller, the small spinning part that moves the water, but getting to it usually means pulling the dishwasher out of its cabinet, which is a bigger job than it sounds like. The machine is heavy, the water lines are connected, and the floor underneath is often unforgiving. This is the point where most homeowners should stop and call an appliance repair technician, especially if the dishwasher is still under warranty, because opening the pump housing can void it. A California appliance repair technician will check the pump the same way, and the visit is usually a short one when the diagnosis is already narrowed down.

Stop and call a New York appliance repair technician if you see water leaking from under the machine, which usually means a hose or a seal has failed, and running the dishwasher will only put more water on the floor. Stop if the dishwasher trips the breaker when it tries to drain, which points to a motor or wiring problem. Stop if you have worked through the filter, the hose, the disposal, and the air gap, and the water is still there, because the next steps involve the pump, the control board, or pulling the machine out, and all of those are easier, cheaper, and safer in experienced hands.

Also stop if the dishwasher is old and this is the third problem in a year. A drain pump replacement on a machine that is already on its last legs is money that might be better spent on a replacement, and a good technician will tell you that honestly if you ask. A Los Angeles appliance repair technician who has seen the inside of your machine can answer the repair-or-replace question better than any guide, because they can see the condition of the parts around the pump too.