Your Dishwasher Filter Is Disgusting: Here’s How to Clean It

There are two kinds of basic dishwasher design, the filter and the macerator. If you don’t know which one you have, and you’ve never opened it up to clean it/check it out, then you may be in for a very nasty surprise. Filter-based models need to have their filters cleaned regularly. If you’ve never cleaned yours, then you have years worth of food slurry built up in there. 

Box of Delights

A dishwasher is just a box with a couple of spray arms inside. Water gets pumped in through those spray arms, and forces them to spin. But it doesn’t constantly spray fresh water. That would be a waste of both water and the electricity needed to heat it. Instead, it recycles the water for a while, pumping the same dirty water through the spray arms for the length of a cycle, before draining it out, and starting over with fresh water. 

In order to stop chunks of food blocking the holes in the spray arms, the dishwasher will use either a macerator or a filter. The macerator works like the garbage disposal in a sink, and uses whirring blades to liquidize food chunks. A filter uses a mesh cylinder in the bottom of the machine to hold back those chunks. Some of the food waste will still get mashed to a pulp and get washed out, but some of it will build up in the mesh filter. 

So why use filters at all? Two reasons. They’re cheaper to install, with no moving parts. And they’re quieter, because you don’t have a blender whirring away at the bottom of your dishwasher. And to be honest, if you clean them regularly, they’re not really any more hassle than the macerator kind. Not cleaning them will lead to a buildup of gross goo, and may even end up flooding the dishwasher if it cannot drain.

How to clean your dishwasher’s filter

First, check to see if you have a filter. Actually, first you should open a window, and prepare yourself for the worst. Then, roll out the bottom dishwasher rack and take a look. You’ll see the cap for the salt container, and if you have a filter, you will also see something like the photo below, a metal mesh plate with a plastic ring set into it. Twist that ring to release the filter assembly and lift it out. You’ll see any bad news immediately.

On my second-hand Bosch dishwasher, you just pop the cylindrical filter off the bottom of the assembly and clean everything up. Other brands may use a removable “cartridge” that can be separated from the surrounding metal mesh pane. With these, be careful that you don’t snap off any plastic retaining tabs during removal and replacement.

To clean the filter assembly, I use a stiff bristle brush, the kind some people use to wash pots, and a little running water. You can use dish soap too, but it might not be necessary, depending on how greasy things are in there. Also scrub the rest of the assembly, especially the metal mesh that forms the top surface. 

Then turn your attention to the newly-opened hole in the bottom of the dishwasher. If this is the first time you’ve opened up the filter assembly, you’ll probably need to give it a deep clean. For ongoing maintenance cleaning, you may just need to wipe it out from time to time. 

How often do you need to clean the filter? I’ve gotten into the habit of checking it after every wash. Or rather, I check it when the dishwasher is full of dirty dishes, and ready to roll. This also means I clean any food that has fallen to the bottom and wound up on top of the filter, which means less gunk right from the start. 

Depending on your dishwasher, and how well you scrape your plates before loading, you may get away with less. But if you have a filter, you do need to clean it regularly. To begin with, check every time like I do, and you’ll soon see how much filth build up in there after each run. And if your dishwasher still smells bad after your filter cleanup, try our dishwasher smells troubleshooting guide.

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Other Dishwasher Maintenance Tips

Other than the filter, a dishwasher does a pretty good job of keeping itself clean, but that doesn’t mean you never have to give it a helping hand, and we have iFixit repair guides for 28 dishwasher brands. Once in a while you should run it on a self-cleaning cycle, empty of anything but the dishwasher’s own racks. You can buy special dishwasher cleaners for this, or just use cleaning vinegar and regular dishwasher detergent. 

Those commercial cleaners are essentially just vinegar, but the clever part is in the packaging. The slim slab should slot between the rods in the dishwasher rack to keep it vertical. And the neck of these square plastic bottles is plugged with wax (remove the foil protective layer first). That wax is essentially an analog timer which melts when the water gets hot. This keeps the bottle from emptying its payload until the main cycle has commenced, for maximum contact time in the machine. More on this in the final section.

Even with the filter and/or macerator, stuff can still block the holes in the spray arms, so it’s good practice to check those holes once in a while. The most common culprit in my dishwasher is those little sticky labels you get on fruit. These end up blocking the last, outermost holes in the rotors. I pick them out with tweezers, but if you find anything else jammed in there, the only option might be to just poke it back in and check again later to see if it has worked its own way through. 

You should also check the water-supply connector at the back of the top rack. There’s a hole in the back wall of the dishwasher which mates with the pipe running from the pipe that runs along the bottom of the top rack, and carries water to the spray arms. This connection seals up when you push the top rack back in. Check and clean both sides of that connection. 

Also remember to top up the salt in your dishwasher. Salt is used to soften the water, to stop limescale build-up on your dishes and glasses, and in the machine’s mechanism itself. The frequency of salt top-ups will depend on the hardness of the water in your area, so get used to checking regularly until you know its rhythms. Dishwasher salt is the same as regular salt, only it comes in bigger granules to prevent clogging. If you already have soft-enough water, you may not need salt. You can buy a hard-water test strip to check.

Also, just clean the dishwasher from time to time with a cloth. Gunk will build up in corners, and under lips, and around the rubber door seals—which you should also check to make sure they are clean, and can still seal the door.

… and a Game-Changing Dishwasher Hack

As hinted at above, a dishwasher will typically run through a few cycles of water. The first one is short, and is designed to get the leftover chunks and smears off the plates, and out of the dishwasher. The second cycle is the longest, and relies partly on the efficacy of the first cycle so that it’s not just spraying thick slurry over your plates for two hours.

The final cycle is the rinse cycle, a short cycle with hot clean water. These cycles can vary depending on the machine, and which program you choose, but that’s the general order of things.

The problem here is that the little hatch that holds your dishwasher detergent/tablet—the one in the door—doesn’t open until the main cycle. This means that the dirtiest first cycle, the one meant to clear as much gunk as possible, has to run without soap. This can leave plates greasy and dirtier than necessary. 

The trick is to get some soap into that first cycle. I do this by squirting some of the detergent dose onto the inside of the door, so it’s right there at the beginning. You could also break off some of the tablet if you use those, but I’d recommend using liquid. It’s cheaper, and you can decide exactly how much you use (and you should definitely try using less than the manufacturer recommends, too). 

This trick—using some of the detergent for the initial cycle—can make a drastic difference to the results, without using any extra detergent. 

There is no reason that a well-maintained dishwasher shouldn’t keep washing perfectly for its entire life. And by keeping it clean and limescale-free, you will be extending that life, perhaps quite considerably.