How to Clean a Dishwasher

A dishwasher washes everything except itself. Food soil, grease and dissolved minerals all end up somewhere inside it, and the machine only removes what the filter and the drain can carry away. This is the routine that keeps ours running, in the order that matters.

The Monthly Ten Minutes

1. The filter

Modern dishwashers dropped the food grinder and use a filter instead, which is why they are quieter and why they need this. Open the door, take out the lower rack, and look at the base: most machines have a cylindrical filter that twists out, often with a flat mesh plate underneath it. Twist, lift, and take both to the sink.

Rinse under running water, use a soft brush and a drop of washing-up liquid on the mesh, and check the fine perforations are actually open against the light. Refit it the right way round and make sure it locks: a filter left loose lets debris straight into the pump, which is the failure this whole routine exists to prevent.

2. The spray arms

Spin each arm by hand. It should turn freely. Then look at the jets: hard water and small food particles block them, and a blocked jet leaves a dry shadow on the dishes above it. Clear any blocked hole with a pin or a piece of wire, and if the arm lifts off easily, take it off and rinse the inside out under the tap.

3. The door seal and the edges

Wipe the rubber seal all the way round with a damp cloth, paying attention to the underside and the corners at the bottom, where a black film builds. Wipe the door edge and the lip of the tub that the seal presses against, and the detergent dispenser flap. These are the spots that hold the smell people blame on the drain.

The Descaling Cycle

Every month or two, run the machine empty and hot with a descaling agent. What you use matters less than doing it, but there is a hierarchy.

Run the longest, hottest cycle available with the machine empty apart from the cleaner. Skip the drying phase if your machine lets you: the point is contact time with hot acidic water, not heat afterwards.

In a hard-water house this is not optional maintenance. Scale plates onto the heating element, which is the hottest surface in the machine, and a scaled element takes longer to reach temperature, extends cycles and eventually fails. That mechanism is the main reason dishwashers fall short of their published nine-year life, and it is covered in what hard water does to a dishwasher.

Twice a Year: the Drain Path

• Clear the sump. With the filter out, sponge any standing water from the well and look for glass fragments, seeds and labels from jars, which are the classic pump-killers
• Check the drain hose has a high loop. It must rise above the level of the sump before it reaches the trap, or waste water siphons back into the machine and sits there between cycles
• Clean the air gap if you have one on the worktop: unscrew the cap, lift the cover, and clear the debris inside it
• Run hot water at the sink before starting a cycle, so the machine draws hot water rather than the cold sitting in the pipe
• Check the garbage disposal is clear if the dishwasher drains through it, and that the knock-out plug was removed when it was installed, which is a surprisingly common oversight

Smells: Housekeeping or Fault?

This is the distinction worth being clear about, because it decides whether cleaning will help at all.

The second row is the one people fight for months. If a machine smells again within a day of a thorough clean, water is coming back into it, and no amount of vinegar will change that. Across 64 completed dishwasher repairs in our own book the median finished job came to $299, with the middle half between $250 and $375, and drain-side work sits at the lower end of that range.

Loading Habits That Keep It Clean

• Scrape, do not rinse. A soil sensor reading clean water shortens the wash, and enzyme detergents need something to work on. Rinsing plates to a shine is the most common self-inflicted cause of poor cleaning
• Do not nest items. Two bowls stacked shield each other, and the shadowed one comes out dirty
• Keep tall items off the top spray arm. A pan handle stopping the arm turning ruins the whole load
• Load plates facing the centre, so the jets hit the soiled face rather than the back
• Do not overfill. A packed machine is the second most common reason for gritty dishes
• Use the right detergent dose for your water hardness, and keep rinse aid topped up so water sheets off instead of drying as spots

The full diagnostic sequence for dishes coming out dirty is in why a dishwasher stops cleaning properly, and the pre-rinsing question in how much water a dishwasher uses.

What Not to Do

• No bleach in a stainless machine. It attacks the tub, the fasteners and the seals
• No dishwasher tablets as a descaler. They are detergent, not acid, and they do nothing to scale
• Do not run a cleaner with dishes inside. Concentrated acid and crockery is a bad combination, and the cycle is meant to be empty
• Do not power-wash the filter mesh with anything abrasive; a torn filter passes debris straight to the pump
• Do not leave the door shut tight for days. A closed damp box grows exactly what you are trying to remove: leave it ajar
• Do not ignore glass fragments in the sump. They find the pump impeller eventually

When Cleaning Will Not Fix It

Some symptoms are mechanical from the start, and recognising them saves a month of experiments.

• Standing water in the sump every morning after the cycle finished: drain geometry, a failed check valve, or a pump
• Dishes barely warm at the end: the heating element or its control, and the cycle will have been getting longer for a while
• White etching on glass that does not wipe off: permanent damage from soft water and over-dosed detergent, not scale
• Grit after a proper filter clean: a weak circulation pump or a blocked arm feed
• Rust at the base of the tub or around the door frame: the coating has gone, and that is a machine at the end of its life

Where a machine sits in its life expectancy changes what is worth repairing, and that is set out year by year in how long dishwashers last.

Film or Etching: Two Faults That Look Identical

Cloudy glassware is the complaint that sends most people looking for a cleaning routine, and half the time cleaning is the wrong answer, because there are two entirely different causes with opposite fixes.

Film is mineral deposit sitting on the surface. It comes from hard water and too little detergent for that hardness, and the test is simple: soak the glass in white vinegar for a few minutes, or rub it with a little citric acid solution. If it clears, it was film, and the fix is more detergent, rinse aid and regular descaling.

Etching is the glass itself being eaten, and it is permanent. It comes from the opposite conditions: soft water, too much detergent, and very hot cycles, which together strip minerals out of the glass surface. If vinegar does nothing, the damage is etching and no product will reverse it. The fix is preventative, for the glasses you still have: reduce the detergent dose, use a cooler programme and skip the pre-rinse.

Getting this the wrong way round is common and expensive in glassware. People with etching often add more detergent, which accelerates it, and people with film often reduce detergent, which makes it worse. Do the vinegar test before changing anything.

What a Clean Machine Should Look Like

• The filter mesh passes light when you hold it up, with no felted layer across the perforations
• Both spray arms spin freely with a flick of a finger and every jet is open
• The sump is dry a few hours after a cycle, with no standing water
• The seal is flexible and pale on the underside, not tacky or black in the corners
• The heating element looks like metal, not like a chalky white rod
• The detergent flap snaps shut and opens freely, without residue holding it

If all six are true and the machine still underperforms, the problem is mechanical and worth a diagnosis rather than another cleaning product.

If water is still sitting in the tub after a cycle, cleaning will not solve it on its own: dishwasher not draining covers the filter, the sump, the hose and the high loop.

A smell that survives cleaning often lives in the drain hose rather than the tub, where sags hold standing water between cycles: the dishwasher drain hose.

If a smell keeps coming back, the debris is sitting in standing water rather than on the tub walls: water in the bottom of a dishwasher.

Older Whirlpool-built machines have no removable filter at all — a food grinder does the work instead, which changes the maintenance entirely: Whirlpool dishwasher not draining.

What the residue itself looks like points at the cause — grit, grease, chalk and etching are four different problems: Whirlpool dishwasher not cleaning.

Frequently Asked Questions