Why Is My Dishwasher Not Draining?

Quick answer: A dishwasher not draining is usually a blocked filter, and that is a ten minute job. Water left in the bottom of a dishwasher is caused by a blocked filter, a kinked or blocked drain hose, a garbage disposal knockout plug that was never removed, or a failed drain pump. Clean the filter first, then check the hose behind the machine has a high loop and is not crushed. A machine that hums during the drain phase but moves no water usually has something jammed in the pump.

Key Takeaways

• A thin film of water in the filter recess is normal. Water across the floor of the tub is not.
• The filter is the first and most likely cause, and it lifts out with a quarter turn.
• On a new installation, the missing disposal knockout plug is the classic cause and catches many people.
• Standing water goes stagnant fast, so a drainage fault turns into a smell within a day or two.

Dishwasher not draining? Clear the water first

Scoop out what you can with a cup, then soak up the rest with towels. Work with an empty tub, because everything below is easier to see and safer to handle without dirty water in the way.

Take the bottom rack out and leave it out while you work.

1. The filter

In the floor of the tub there is a cylindrical filter with an arrow or a padlock marking. Twist it anticlockwise and lift it out, then lift out the flat mesh screen beneath it.

Rinse both under hot running water and scrub the mesh with an old toothbrush. Look into the recess underneath as well, since food that gets past a loose filter collects in the sump.

Refit with the same quarter turn and make sure the tower locks. A filter left loose sends debris straight into the pump, which converts a free fix into a repair.

This alone resolves a large share of drainage complaints, and it is why the filter is the centrepiece of how to clean a dishwasher.

2. The drain hose

Pull the machine forward gently and look at the corrugated hose running from the back to the sink cabinet.

Two things matter. It must not be crushed or kinked, which happens when the machine is pushed back into a tight space. And it must rise into a high loop, fixed up under the counter above the level of the tub, before it drops to the waste connection. Without that loop, waste water siphons back into the dishwasher, which both stops it draining properly and brings the drain smell with it.

A hose can also block internally with grease and debris, usually right at the bends. That needs disconnecting and flushing.

3. The garbage disposal plug

This one catches a lot of people and costs a service call that was never needed.

When a dishwasher drains into a garbage disposal, the disposal ships with a knockout plug sealing the dishwasher inlet. Whoever installs the dishwasher is supposed to punch that plug out. When it is missed, the dishwasher has nowhere to pump to and the water simply stays in the tub.

The tell is timing: a brand new dishwasher, or a newly replaced disposal, that has never drained properly since day one. An appliance that worked for five years and stopped is a different problem.

While you are there, run the disposal. A disposal full of food waste will also stop a dishwasher draining.

4. The drain pump

With the filter clear, the hose clear and the disposal sorted, the pump is what is left.

Listen during the drain phase. A loud hum or buzz with no water movement means the motor is energised but the impeller is jammed, usually by glass, a fruit sticker, or a piece of bone. Silence during the drain phase means the pump is not running at all, which can be the pump itself or the control board telling it to.

Either way the machine has to come apart, and there is broken glass involved often enough that it is worth having someone do it who is set up for that.

What not to do

Do not pour drain cleaner into a dishwasher. It is formulated for sink traps, not for a machine full of rubber seals, plastic and an aluminium pump housing, and it can do real damage.

Do not run the machine repeatedly hoping it clears. If the pump is jammed you are heating the motor windings for no reason.

Do not pull the machine right out of the cabinet and start disconnecting things before someone arrives. Leaving the fault exactly as it is makes it quicker to find, which is most of the reason our jobs usually finish in a single visit.

Frequently asked questions

Is a little water in the bottom normal?

A shallow film in the filter recess is normal and keeps the seal from drying out. Water covering the base or standing above the filter is not.

Can I use vinegar and baking soda to unblock it?

It will not clear a mechanical blockage. It is useful for smell and light residue, which is a different problem from a machine that will not drain.

Why does it drain but leave dirty water?

Usually a partly blocked filter that lets the pump work but recirculates debris. Clean the filter and the spray arms together.

My machine shows an error code. Does that change anything?

It narrows it down. Note the exact code before switching the machine off, since it saves diagnostic time. Codes that return after a power cycle are real faults rather than glitches.

Is a drain pump worth replacing?

On most machines yes, it is a common part and a routine repair. On a very old dishwasher where the part is discontinued, it may not be, and we will say so rather than take the job.

Where to go from here

Standing water is the usual reason a machine starts to smell, covered in why a dishwasher smells bad. If water is ending up outside the machine instead, see five reasons a dishwasher leaks. Poor results have their own causes in a dishwasher that is not cleaning properly. The washing machine equivalent is a washing machine not draining or spinning, and the logic is nearly the same.

To book, see dishwasher repair in Winnipeg.

Elsewhere on the site: what to do before a technician arrives.