Cleaning the Filter in a Bosch Dishwasher, and How Often It Really Needs It

The part nobody was told about

Open the door of your dishwasher and take the lower rack out. In the floor of the tub is a cylindrical plastic assembly, usually with an arrow on it.

That is the filter, and it unscrews by hand.

It needs cleaning about once a month. Almost nobody does it, because almost nobody has been told, and the single most common repair call we take on this brand is a machine that will not drain — which is what happens after a year or two of not doing it.

The five-minute version

1. Lower rack out.
2. Twist the filter counter-clockwise and lift it out. No tools. If a tool seems necessary, see the last question below.
3. Separate the parts. Most assemblies split into a cylinder and a flat mesh plate. Debris collects between them, out of sight.
4. Rinse under a tap with a soft brush and a little washing-up liquid. A nail brush is perfect. Rinsing alone leaves the grease film that is doing most of the blocking.
5. Lift the pump cover beside it and clear what is underneath — this is where the glass fragments and fruit stickers end up.
6. Screw the filter back until it seats. Hand-tight, and make sure it turns home rather than sitting proud.

How often, honestly

• Monthly for a household running the machine most days, scraping plates before loading.
• Every two weeks if you run short or eco cycles most of the time. Those cycles are cooler, and cooler water carries less grease away — more of it stays on the filter.
• After anything unusual. A party, a roasting tray, a load with a lot of rice or pasta. Those are the loads that block a filter in one go.

What a blocked filter looks like from outside

You will usually notice one of these before you notice the filter:

• Grit on glasses and inside cups. Food that cannot leave the machine being redistributed over the load. This is the classic and it is unmistakable once you know.
• Water standing in the tub after a cycle, or draining more slowly than it used to.
• A smell when you open the door, especially after the machine has sat unused for a few days.
• A code in the twenties, or four lights flashing on a machine with no display. By then it has been blocked a while.

While you are down there

Two other things take another two minutes.

The spray arms. Spin each by hand with the racks in place. They should turn freely. If a knife handle or a baking sheet stops one, that is a cleaning problem with a loading cause. Hold an arm up to the light and look at the jets — blocked ones show immediately and clear with a toothpick.

The door seal. Run a finger along the bottom lip and into the channel. What comes off on a cloth is usually surprising, and it is where dishwasher smells live.

What ends up in there, and what it tells you

The contents of a filter are a surprisingly good report on how the machine is being used.

Soft sludge, evenly spread. Normal. A month of ordinary cooking, and it rinses off in seconds.

Whole pieces of food. Plates are going in with too much on them. Scrape rather than rinse — scraping keeps the filter manageable, and rinsing tells the machine the load is clean and gets you a short cool cycle you did not want.

Grease that has set hard. The machine is not getting hot enough often enough, which on a household running eco cycles exclusively is common. One hot cycle a week changes it.

Seeds, rice, coffee grounds. Small enough to pass the coarse screen and exactly the right size to mat across the fine one. Nothing to fix; just clean it more often.

Grit and sand. Unusual, and worth mentioning to us. It sometimes points at deposits breaking loose from inside the machine rather than coming off the plates.

The mistake that puts it back wrong

The filter assembly has to seat and lock, and it turns further than people expect. If it is proud by even a couple of millimeters, debris goes past it and straight to the pump — which is how a machine that was cleaned last week arrives with a blocked drain this week.

Turn it until it stops, then check by trying to lift it. It should not move.

The same applies twice over to the drain pump cover beside it: it clicks, and a cover that has not clicked is a cover that lets the pump draw air.

What a monthly filter actually prevents

• The drain call. The most common repair we are asked for on this brand, and the one most often caused by a filter left for a year.
• Grit on the glassware, which people usually blame on detergent.
• Smells, which live in what the filter is holding.
• The pump itself. Debris that gets past a blocked filter ends up at the impeller, and clearing a jammed pump is a visit rather than five minutes.

None of that is dramatic. It is simply the difference between an appliance that gets serviced for free by its owner every month and one that gets serviced by us once a year.