Why is My Dishwasher Not Draining?

Water failing to drain is one of the most common problems that people have with their dishwashers. It’s also an issue that’s easy to diagnose, with standing water in the basin being the obvious symptom.

There are several different reasons that this fault can arise, but fortunately in the majority of cases a simple blockage is the culprit – usually an easy fix that won’t require replacement parts or an engineer call-out.

If your dishwasher has detected a drainage problem it will stop the wash cycle which will prevent any flooding/leaking, and display an error code which might give you a clue as to the source of the fault.

You can find fault code definitions for your make/model of dishwasher by selecting a manufacturer from this list.

Is the Dishwasher Filter Blocked?

If your dishwasher isn’t draining properly then checking the filter in the sump should always be your first course of action – it’s the most common cause and the easiest to fix.

How to Remove and Clean Your Dishwasher Filter

  • First remove the lower basket from the dishwasher.
  • Next remove the central filter by twisting it anticlockwise and lifting out.
  • The larger mesh filter should now lift out easily.
  • Separate the central filter into its two component parts.

Now give the filters a good clean, removing any food debris and washing all the parts in warm soapy water. The larger mesh filter can often get clogged up with fat residue and other gunk. If that is the case pour some boiling water over it and then wipe it down.

Before replacing the filters have a look in the sump (where the central filter was sitting) and check to make sure no food debris has worked its way down there. If it does look to be clogged up then try and clear the blockage.

Once the filters are clean and you’re satisfied that any blockages have been cleared you can refit the filters – first the large mesh filter, then insert the central filter and twist clockwise until it locks into place.

Over time the filter will inevitably get clogged up with food debris and will need cleaning out again. The problem can be exacerbated if you frequently use economy/short wash programs as the cooler water temperature makes it easier for debris and residues to clog up the filter – try running a full/hot cycle every few days to help clear any buildup.

Other Types of Blockage

If your dishwasher still isn’t draining after ensuring the filter and sump are clear then there could be a blockage elsewhere.

The dishwasher waste pipe is a good place to check next and the easiest place to get access is where it connects to the pipework under your kitchen sink.

It’s unlikely that any large pieces of debris have managed to find their way down the outlet, but as the water leaving the dishwasher cools down any grease or fat traveling along the pipe can begin to solidify and cause a blockage.

Before disconnecting anything it’s worth giving the hose a squeeze and a wiggle to see if you can break up any solids, and then running the dishwasher on its hottest program to wash away any remnants.

If the blockage is too stubborn to be shifted by the aforementioned squeeze and wiggle then the next step is to disconnect the waste pipe in order to find and clear the blockage (a plumbers snake is the best tool for this kind of job, and not very expensive).

As with filter blockages, you can avoid the outlet from becoming blocked in the future by regularly running the dishwasher on a hot washing cycle which will help clear away any residue buildup.

Dishwasher Drain Pump Failure

If it doesn’t seem like a blockage is causing the problem, then a drain pump fault is the other common reason for a dishwasher not draining.

If your dishwasher drain pump has failed then the good news is that replacement pumps are inexpensive. The bad news is that getting access to the pump can be a pain, although nothing beyond the scope of a competent DIYer.

The pumps (wash and drain) on a dishwasher obviously have to be connected to the sump in someway and are therefore always found at the bottom of the unit. You can usually get at them by removing the panel below the dishwasher door (it’s easier to gain access if you are able to tip the dishwasher backwards).

Once you have access to the underside of the dishwasher it will be easy to spot the drain pump (it’ll be the smaller of the two pumps) and will just be attached to the base with some screws or a simple twist-lock. Space is very tight however so getting your hands in to remove the pump can be fiddly and frustrating.

Before buying and fitting a replacement part it’s worth checking the drain pump for any obstructions that could have caused it to jam – it’s not all that uncommon and could save you having to splash out on a new pump.

Still Stuck?

A blockage or drain pump failure are the cause of a dishwasher not draining properly in 99% of cases. If the fault is being caused by something else then the odds are you’ll be unable to diagnose and fix the problem yourself and you should get in touch with a professional engineer.