Dishwasher not draining? Start with the filter, then these three causes

Water sitting in the bottom at the end of a cycle is a fault most dishwasher owners meet eventually. The good news is that a dishwasher not draining is usually caused by the one part you can reach without tools. Work through the checks below in order and you will either fix it in ten minutes or know exactly what to tell us when you ring.

Why is my dishwasher not draining?

Most of the time it is a blockage, and the blockage is in the filter. Bosch’s own support material says the most common reason a dishwasher stops draining is food debris caught in the filter or the pump, and CHOICE reaches the same conclusion about a filter that has not been cleaned.

The four usual causes, in the order they turn up:

1. A blocked filter. Grease, labels off jars, seeds, rice and bits of food build into a mat that water cannot get through.
2. A blocked or kinked drain hose. Often behind or under the machine, sometimes squashed when the dishwasher was pushed back into its cabinet.
3. A blockage in the sink waste, not the dishwasher at all. The dishwasher usually drains into the same waste as your sink.
4. A drain pump with something jammed in it. Broken glass and grit are the usual culprits.

One thing worth knowing before you start pulling things apart. A shallow pool of water sitting in the sump, below the top of the filter, is normal on a lot of machines and is not a fault. Water sitting above the filter, or enough to cover the bottom of the tub, is.

How do I clean a dishwasher filter?

Twist the cylindrical filter anticlockwise, lift it out, wash it under hot water with a soft brush, then refit it and lock it back in. It takes about ten minutes and it is the single most useful thing you can do for a dishwasher.

Then work through it in this order.

1. Bail the water out. Scoop it into a bucket, then soak up the last of it with a towel. You need the tub dry enough to see what you are doing.
2. Take the bottom rack out and remove the filter. Most are a cylinder that twists out, sitting in a flat mesh screen. Lift both. Check your manual if yours does not come away easily, because forcing it can crack the housing.
3. Wash both parts in hot soapy water with a soft brush. Grease is what holds the debris together, so it needs hot water, not a rinse.
4. Look into the empty housing. The drain pump impeller sits at the bottom. Clear anything caught in there.
5. Refit the filter and lock it, then run a short cycle with the machine empty and watch whether it drains. A filter that is not seated properly causes its own drain fault.

CHOICE recommends cleaning the filter every month as ordinary maintenance. Almost nobody does, which is why it heads this list. A filter left alone for years does not just block itself, it lets debris wash through to the pump behind it.

Is the blockage in the drain hose or the sink?

If the filter was clean, or cleaning it changed nothing, the blockage is further along.

Check the drain hose. It runs from the back of the dishwasher to the plumbing under the sink. Look for a kink, a squash point where the machine was pushed back into its cabinet, or a sagging section. Electrolux lists a blocked or pinched hose among the first things to check when a machine reports a drain fault.

Check the high loop. The hose should rise high under the bench before dropping to the waste. That loop stops dirty sink water siphoning back into the machine. If it has slipped down, the dishwasher can look like it is not draining when it is actually refilling itself from the sink.

Then check the sink. Fill it, pull the plug, and watch. If the sink is slow, the dishwasher was never the problem, and the same goes for a food waste disposal that has not been cleared. Two minutes here can save you a callout that gets you nowhere.

New installations are their own category. A drain fault in the first few months is usually the installation rather than the appliance: a hose that is too long, a loop that is too low, or a waste connection that was never opened up properly.

How do I know if it’s the drain pump?

Listen to it. A working drain pump makes an obvious whirring noise for around thirty seconds partway through the cycle. If you hear nothing at all, or you hear a hum with no water moving, the pump is where the fault is.

Two things go wrong with drain pumps. Something jams the impeller, or the pump fails outright.

The jam is far more common, and broken glass is the usual reason. A glass chips in the rack, the fragment washes down past the filter, and it wedges the impeller so it cannot turn. Grit, fruit stickers and small bones do the same job. Miele’s guidance on its own drain fault is to check the impeller turns freely and that the non-return valve sits flush, which describes what goes wrong on any brand.

If the impeller is clear and turning and the pump still does nothing, the pump itself has failed. That is a replacement part rather than a clean, and it is where the job stops being a DIY one. Our service van is stocked with parts, which is why most dishwasher repairs are finished the day we arrive rather than on a second visit.

Nothing’s blocked and the dishwasher is still not draining

If the filter is clean, the hose is clear, the sink drains and the pump turns, the fault is electrical rather than mechanical. Three candidates:

• The drain solenoid or valve. On some machines a valve has to open before the pump can push water out. If it stays shut, the pump runs and nothing moves.
• The control board. It tells the pump when to run. A failed board means the pump never gets the signal, which sounds exactly like a dead pump from the outside.
• The wiring to the pump. Less common, and the one a licensed electrician is best placed to find.

None of these can be diagnosed by looking. They need a meter and the machine opened up, which is fixed electrical work on a hardwired appliance. Your technician is a licensed electrician, NSW electrical licence 337447C, as well as an appliance repairer, so a fault that turns out to be the circuit rather than the machine is still the right call. We work across most brands we repair.

Drain error codes on the main brands

If your dishwasher shows a code, it narrows things down. Here is what the drain-related codes mean, taken from each manufacturer’s own documentation.

Two honest notes on that table.

Fisher & Paykel has no drain-specific code on its built-in dishwashers. Its published F codes cover flooding, water flow, electronics, power supply and the motor. A machine that will not drain often shows nothing at all, which catches people out.

Bosch and Asko do not publish what their codes mean. Bosch dishwashers show an E code, but Bosch’s public support material goes straight to the filter and the pump rather than explaining the number, so your manual is the authority. Miele dishwashers are the opposite, with the fault documented properly on Miele’s own site.

Either way, a code tells you where to look, not what has failed. The same code can come from a blocked filter or a dead pump.

How long should a dishwasher last?

Around nine to ten years, and replacement starts to make more sense from about six and a half to eight years, according to CHOICE’s figures for Australian households.

That number changes the conversation. A drain fault at year three is a nuisance on a machine with most of its life ahead of it. The same fault at year twelve is worth thinking about, particularly if something else has already gone wrong.

Is it worth repairing a dishwasher that isn’t draining?

Usually yes. Drain faults are the good kind of fault, because the parts that fail are wear parts rather than major assemblies. A filter costs nothing to clean, a hose is cheap, and a drain pump is one of the less expensive parts in the machine.

It stops being worth it when the drain fault sits alongside something else. A failed control board on a mid-range machine can approach the value of the appliance, and a machine already past its expected life with two faults is telling you something. If it is not worth fixing, we will say so before you spend another dollar. Our guide to repair or replace sets out how to weigh that up.

On cost. We charge a service call fee and we will tell you exactly what it is when you ring. No hidden extras. Every repair is backed by our 12 month warranty on parts and labour, so if the same fault comes back, so do we.

On your rights. If your dishwasher failed earlier than it reasonably should have for what you paid, you may not need to pay for the repair at all. Consumer guarantees under Australian Consumer Law are automatic, cannot be removed by a business, and include durability. Those rights are held against the retailer you bought from, and they sit above any warranty, ours included. Our 12 month warranty is an extra promise on top of them, never a replacement for them.

Common questions

Should I run the dishwasher if there’s standing water in it?

No. Another cycle just adds water and detergent to what is already sitting there, and it can push water past the door seal onto your floor. Bail it out and find the blockage first.

What can I put in my dishwasher to unclog the drain?

Bicarbonate of soda and vinegar is the usual suggestion, and it does have a use. It softens greasy build-up in the filter and the sump. It will do nothing at all for a piece of glass jammed in the impeller or a kinked hose. Treat it as a cleaning step after you have cleared the filter, not as a fix on its own.

How do you force a dishwasher to drain?

Most machines have a drain or cancel function that runs the pump on its own, though the button combination differs by brand, so check your manual. If the pump runs and the water still goes nowhere, you have confirmed the blockage sits downstream of the pump.

How often should I clean the filter?

Monthly. It takes ten minutes and it prevents most of what is on this page.

We repair dishwashers across the Central Coast, from Patonga to Berkeley Vale, along with everything we repair.