How to Clean a Dishwasher: Filter, Spray Arms & Seals

Your dishwasher washes the dishes, but nothing washes the dishwasher. Food scraps collect in the filter, grease coats the walls and seals, limescale blocks the holes in the spray arms, and detergent residue builds up in the places the water never properly reaches. The signs are familiar: a stale smell when you open the door, cloudy glasses, gritty plates, a puddle left in the base, or a cycle that seems to run longer than it used to.

Most of those problems come from three places, in this order: the filter, the spray arms and the door seal. A cleaning cycle only does part of the job, so the hands-on work comes first and the cycle comes second. Below is a quick comparison of the main ways to clean a dishwasher, then each job in order, with the limescale, smell and schedule questions covered afterwards.

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Four ways to clean a dishwasher, compared

If you only do one thing, clean the filter. If the machine is in hard water territory and the walls or heating element have a white crust, add a citric acid or descaler cycle. If it smells, the filter and the door seal are the first suspects, followed by the drain. Vinegar sits last in the table not because it never works, but because it is the one most likely to cause harm if used too often, so check your manual before making it a monthly habit.

The hands-on part: filter, spray arms, seals and racks

Start with an empty dishwasher. Take out the racks and the cutlery basket, and look at the base for anything large. Bottle tops, bits of broken glass or china, labels and olive stones all collect in the corners and block the drain or jam the spray arms. Wear rubber gloves for this, because the filter area holds old food and sharp pieces. You will need an old toothbrush, a bottle brush, a cocktail stick or straightened paperclip, and a few cloths. A bottle brush and detail brush set is handy for the inside of spray arms.

Before you start, switch the machine off at the socket and let the door stand open until the inside is cool, particularly if it has just finished a hot cycle. Lay a towel on the floor in front of the door, because the filter housing and the spray arms always drip. Use plastic or wooden tools such as a cocktail stick on the spray-arm holes, and avoid metal scourers or knives anywhere inside, because scratches in the tub or on plastic parts collect grease and make the next clean harder. If you are unsure how a part comes out, the manual or the manufacturer’s website usually has a diagram.

The filter

The filter catches food so it does not clog the pump and drain. It is the single most important part to keep clean, and it is the part most owners never look at. It sits in the base of the tub, usually under the bottom spray arm. On most machines it is a cylindrical mesh that twists out, often anticlockwise, and many have a coarse outer filter and a fine mesh inside, so separate both. Check your manual for the exact mechanism, because it differs between makes.

1. Rinse the filter under hot running water, then scrub the mesh with a toothbrush to remove grease and stuck-on food.
2. Look into the housing below it and remove anything lodged there with a cloth or gloved fingers.
3. For baked-on residue, soak it for fifteen minutes in hot water with washing-up liquid, or overnight with a spoonful of bicarbonate of soda, then brush it clean.
4. Check that water runs freely through every part before you refit it, and make sure it is seated and locked properly.

Never run the dishwasher without the filter in place. Debris will go straight to the pump, and some machines will not start without it. A quick rinse after heavy use takes less than a minute, and a full scrub every couple of weeks is plenty for most households. You need to act sooner if dishes come out gritty, water pools in the base after a cycle, there is a smell when you open the door, or the cycle seems to take longer than normal.

If the filter will not come out

Some dishwashers have a fixed filter that is not meant to be removed, so check your manual before you pull. For a removable one that feels stuck, make sure you are turning in the right direction, wiggle gently while you turn rather than forcing it, and look for a release catch or a second locking piece. Running a hot cycle first can soften greasy residue that is making it sticky. If it still will not move, do not force it, since you can strip the thread. Clean fixed filters in place with a brush and a jug of hot water, and contact the manufacturer about model-specific advice.

Spray arms

Spray arms spin as water is forced out of small holes, so even a few blocked holes cut cleaning power. A quick test: run the machine, pause it mid-cycle and open the door carefully, because hot steam will escape. The arms should be spinning freely. When the cycle is finished and the machine is cool, spin each arm by hand. It should rotate smoothly and not catch on anything.

• Bottom arm: usually lifts off or twists anticlockwise, and some have a clip underneath.
• Top arm: often held by a plastic nut in the centre that unscrews anticlockwise.
• Third arm or tray: some models have a spray arm or rail near the top for cutlery, so check before you remove anything.

Rinse each arm under hot water, then hold it up to the light and see which holes are blocked. Clear each hole with a cocktail stick or straightened paperclip, and use a bottle brush to clean inside the arm. For limescale, soak the arms for thirty to sixty minutes in a washing-up bowl of equal parts white vinegar and hot water while you work on the rest of the machine. Soaking is a cheaper and gentler use of vinegar than a full cycle, because it only touches the plastic or metal arms and not the rubber seals. Rinse well, shake out any loose debris and refit them.

What you find tells you what to do next. White crusty deposits are limescale, so soak longer. A sticky film is grease, which needs very hot water and plenty of washing-up liquid. Specks and small particles are food, so clear them mechanically. If an arm still does not turn after cleaning, check the mounting point for debris before assuming it is faulty.

Door seals, edges and racks

Normal cycles do not reach the folds of the door seal, the hinges, the bottom edge of the door or the detergent dispenser area, which is why this is where black mould and slime tend to start. Mix a little washing-up liquid into warm water and wipe all round the seal, working into the folds with a toothbrush. For dark spots, make a paste of bicarbonate of soda and water, scrub gently, then wipe clean with a damp cloth.

Racks can go in the sink or the bath for a soak in hot water and washing-up liquid. Do not put them in a washing machine, as the agitation can damage the rack coating and the drum. Finally wipe the outside with soapy water, including the handle and the control panel, going with the grain on a stainless steel front and drying with a clean cloth to avoid water marks. For more on cleaning appliance fronts, see our guide to cleaning stainless steel, and for more on the filter specifically, our dishwasher filter guide goes into extra detail.

Choosing and running the cleaning cycle

With the filter, arms and seals done, refit everything and run a hot cycle on an empty machine. Which product goes in depends on what you found. Unless the instructions say otherwise, run it with no dishes, no detergent tablet and no rinse aid in the dispenser.

Dishwasher cleaner or descaler

A dedicated cleaner is the simplest option for a neglected machine, because it is formulated for grease and scale together and the packet tells you where it goes: some are poured into the base, some placed in the cup, and some sit on the bottom rack. Follow the instructions on the pack, run the hottest cycle, and do not combine it with vinegar or any other product in the same cycle. Look for a product that says it is suitable for dishwashers and hard water, and read the label for any warning about stainless steel or sensitive finishes. Own-brand cleaners from the supermarkets are usually the same type of product as the big names, so compare the active ingredients and the directions. Browse dishwasher cleaners or a well-known brand of machine cleaner if you want to compare.

Citric acid for limescale

Citric acid powder is a useful middle option for hard water. Many people use three to four tablespoons in the detergent cup or sprinkled in the base of an empty machine, then run a hot cycle. It is generally stronger against scale than vinegar and tends to be gentler on rubber than a long vinegar habit. Check the instructions on the product or in your manual, and use food-grade citric acid sold for cleaning or descaling. Citric acid powder is cheap and keeps for ages in a dry cupboard.

White vinegar, with caveats

A cup of white vinegar stood upright on the top rack of the empty machine, then a hot cycle, is the traditional home method. It helps with grease, film and smells, and it is cheap. The downsides are that vinegar is an acid, and repeated use can dry out or perish rubber seals and hoses, which is why some manufacturers advise against it or recommend a purpose-made cleaner. If your manual does not mention it, using vinegar occasionally is common, but it should not be the monthly default if you have a hard-water scale problem. Our piece on whether vinegar disinfects also explains why it is not a germ-killer.

Pour or stand the vinegar in the machine, not in the detergent dispenser. A bowl or cup on the top rack lets it disperse through the whole cycle. Leave the door ajar for half an hour afterwards so the smell can clear. If you want more on the limescale side, our limescale removal guide explains how acids work on scale.

How long it all takes: a standard hot cycle runs for roughly one and a half to two hours on many machines, though your programme list will tell you exactly. A cleaning cycle with a single product therefore needs a couple of hours, and a full deep clean with two cycles needs three to four hours in total, with only about thirty minutes of that being hands-on. Choose a day when you are at home anyway, and finish by leaving the door open so everything dries, because moisture left behind encourages mould. You will find more tasks that fit around a waiting cycle on our Cleaners Guide home page.

Bicarbonate of soda as a second step

Bicarbonate of soda is mildly alkaline and a gentle abrasive, so it deodorises and lifts light stains. Sprinkle about a cup in the base of the empty machine and run a short hot cycle. The key point: use it in a separate cycle after vinegar, never at the same time. Mixed together the two simply react and cancel each other out, so you lose the benefit of both. Do not follow a commercial cleaner or descaler with bicarbonate unless the product says that is fine.

Never use bleach

Do not use bleach in a dishwasher. It can damage rubber seals and metal parts, leaves residue on surfaces that touch dishes, and releases toxic chlorine gas if it meets vinegar or an acidic cleaner. If you have mould on the seals, a bicarbonate paste is enough. Our list of cleaning products you should never mix explains which combinations are dangerous.

A deep clean for a machine that has never had one

If the dishwasher has gone months or years without attention, plan for three to four hours, most of it waiting. Phase one, thirty minutes by hand: take out the racks and wash them, scrub the filter, soak the spray arms, clean the seals, edges and hinges, and wipe the walls and door. Phase two, while the arms soak: clear every hole and brush inside the arms. Phase three: run a hot cycle with a commercial cleaner or descaler, following the packet. Phase four: run a second hot cycle with citric acid or, if your manual allows it, a cup of vinegar, to help clear residue. Phase five: a short hot cycle with bicarbonate to deodorise. A single hot cycle usually takes between one and two hours depending on the model, so a full deep clean takes most of an afternoon, but your hands are free for most of it. Dry time matters too, so leave the door open afterwards.

For severe cases, treat thick white scale with a dedicated descaler, mould on seals with a bicarbonate paste left on for an hour before scrubbing, and slow draining as a sign that the hose or pump may be partly blocked. If water still does not drain after the filter is clean, our guide to a dishwasher that is not draining covers the next checks.

Limescale, salt and rinse aid in hard water

Hard water is common across large parts of England, particularly in the south and east, and limescale appears as white, chalky deposits on the heating element, the spray arms and the walls. You can check your area on your water company’s website. The signs are white residue on glasses and plates, weaker spray, a visible crust on the element, and a machine that takes longer to heat the water. Scale also makes heating less efficient, which is why it matters beyond looks.

• Mild scale: a citric acid cycle, or a vinegar cycle if your manual allows it. Some people stop the cycle halfway and let the acid sit for a couple of hours before finishing, but check the manufacturer’s advice before doing this.
• Heavy scale: a dedicated dishwasher descaler, used exactly as the packet says.
• Spray arms: soak in neat or half-and-half white vinegar until the scale softens, then clear the holes.
• Heating element: it cannot be scrubbed, so regular descaling cycles are how you keep it clear.

Prevention matters more than treatment. Most dishwashers have a water softener built in, which uses dishwasher salt. Keep that reservoir topped up and set the hardness dial to match your area, using the instructions in the manual. The salt goes only into the softener reservoir, never into the tub, and it must be dishwasher salt rather than table salt. If you use all-in-one tablets in a hard-water area, check whether your machine still needs salt, because some tablets contain it and some do not. Rinse aid, which goes in its own compartment, helps water sheet off glasses and reduces spotting. Dishwasher salt and rinse aid are inexpensive and easy to restock.

Smells, standing water and when it is something else

A smelly dishwasher usually has one of three causes: a dirty filter, food trapped in the door seal, or water that has not fully drained. Start with the filter, since old food rots there. Then scrub the seal folds. If water sits in the base after a cycle, the drain may be partly blocked or the hose kinked, and the standing water goes stagnant. Check the hose is not trapped behind the machine, and see our article on how to clean a drain for the principles of clearing a blocked trap. If you cannot find the problem, a plumber or appliance engineer can check the pump.

A quick way to tell the causes apart: if the smell is strongest when you open the door but the base is dry, think filter and seal. If there is a pool of dirty water in the base after the cycle ends, think drain, hose or pump. If there is a sewer-like smell and the kitchen sink also gurgles, the fault may be in the shared waste pipe or the sink trap rather than in the dishwasher, and a plumber is the right call.

• Scrape plates into the bin before loading. Rinsing is not necessary, but food lumps are.
• Run the machine regularly rather than leaving dirty dishes for days.
• Leave the door ajar after a cycle so moisture can escape.
• If the machine has been unused for more than a week, for example in a holiday home, run an empty hot cycle when you return, since standing water can turn stagnant.
• Do not rely on a lemon in the machine to hide a smell. It can freshen the air slightly, but the filter and seal are what actually need cleaning.

A final point on dishes that still come out dirty after cleaning. If you have cleaned the filter and spray arms and results are still poor, check that you are not overloading the racks, that detergent has not expired or clumped, and that you use a hot cycle at least occasionally. If everything checks out and the machine is still struggling, it may be a mechanical fault, such as a failing pump or heater, which needs an engineer.

How often to clean, and the habits that undo it

How often should you clean a dishwasher, in plain terms? Fortnightly for the filter, weekly for the seals, and a cleaning cycle monthly or quarterly depending on how hard your water is and how heavily you use it. If it starts to smell or the results drop, do it straight away rather than waiting for the next date. Setting a repeating phone reminder on the first of the month is an easy way to remember.

Habits that undo your cleaning

• Too much detergent. Excess does not rinse away completely and leaves cloudy glasses and residue. Use the recommended dose, and a little less if your water is soft.
• Never touching the filter. It does not empty itself, and a clogged one is a common cause of poor results.
• Ignoring the spray arms. The machine can seem to be running perfectly while water barely reaches the dishes.
• Overloading. Dishes crammed together block the arms and stop water circulating. Do not block the detergent dispenser.
• Only using eco or quick cycles. They are fine most of the time, but run a hot cycle now and then so grease does not build up inside the machine.
• Closing the door straight after a cycle. Trapped moisture encourages mould and a musty smell, so leave it ajar.
• Neglecting the seal. Food and grease in the folds rot. Wipe it weekly.
• Skipping salt or rinse aid in hard water. Both help protect the machine and the results.

Two small loading habits help too. Face the dirtiest surfaces towards the spray arms so water reaches them, and unload the bottom rack first so water collected in upturned cups on the top rack does not drip onto clean plates. Our comparison of dishwasher versus hand washing looks at how loading affects results and running costs. If you are cleaning other appliances at the same time, our guide to cleaning a washing machine follows a similar routine.

Can a dishwasher tablet clean your oven?

This idea has gone around social media, and it is a reasonable question for anyone with a spare tablet. The idea is to wet a solid dishwasher tablet and use it like a scrubbing stone on oven glass and interior surfaces, so the tablet dissolves as you rub and lifts grease. It can work on light to moderate grease and on oven door glass, and some stainless steel. It is less good on heavy carbonised build-up, corners and edges, and in large ovens.

Because dishwasher tablets are strongly alkaline and contain detergent chemicals, use gloves, avoid contact with skin and eyes, do not use it on aluminium, non-stick or painted surfaces, and rinse the oven thoroughly afterwards. Do not use it on a self-cleaning oven’s enamel without checking the manual. For heavier grime, a purpose-made oven cleaner or a bicarbonate paste is usually the more sensible choice, and our guide to cleaning an oven covers both. Use a cheap own-brand tablet rather than a premium one if you try this.

The dishwasher cleaning kit, as a checklist

Most of this you probably own already. The list below shows what each item is for and what to look for. Tick off the ones you are missing and compare options through the links, which are Amazon UK searches.

• Dishwasher cleaner: a product that says it is for dishwashers and for grease and limescale, with clear directions for where it goes. Compare dishwasher cleaners and machine cleaner tablets and liquids.
• Citric acid powder: food-grade, sold for cleaning or descaling, useful in hard water and cheaper per use than most descalers.
• Dishwasher salt: coarse granules for the softener reservoir only, never table salt. Only needed if your machine has a softener.
• Rinse aid: improves drying and reduces spots on glasses, and works with the salt in hard water. Browse rinse aid.
• Bottle brush and detail brush: for the inside of spray arms and the filter mesh, with stiff but non-metallic bristles so you do not scratch the tub.
• Rubber gloves: the filter housing holds old food and sharp debris, so a sturdy pair of washing-up gloves is sensible.

Our overall view: a clean filter, clear spray arms and a wiped seal do most of the work, and a cleaner or citric acid cycle once a month or quarter handles the rest. White vinegar and bicarbonate are fine for an occasional freshen up if your manual allows them, but they are not a substitute for a dedicated product when scale is the problem. More cleaning products are listed in our cleaning products section.

Five things people still ask

Why does my dishwasher smell even after cleaning?

Persistent smells usually mean food is trapped somewhere you have not reached, most often the filter housing, the folds of the door seal or the drain. Scrub the filter again, check the seal folds, and make sure water drains fully after each cycle. Then run a hot cleaning cycle with a dishwasher cleaner or citric acid. If standing water remains, check the drain hose for kinks or a blockage.

Why are my dishes still dirty after washing?

The usual causes are a clogged filter, blocked spray arms or an overloaded rack. Clean the filter and clear every spray-arm hole, then load so items do not shield one another. Check that you are using enough detergent and that it has not expired. Run a hot cycle now and then. If cleaning does not help, a pump or heater fault may need an engineer.

How do I remove white residue from my dishwasher?

White residue is almost always limescale. Run a cycle with citric acid or a dishwasher descaler, following the product directions, and soak the spray arms to clear the holes. To stop it coming back, keep the salt reservoir topped up if your machine has one, use rinse aid, and descale regularly. Persistent heavy deposits on the element may call for a stronger descaler.

Can I run a cleaning cycle with dishes inside?

No, unless the product instructions specifically say so. Run cleaners and descalers in an empty machine so the product can reach every surface and so you do not leave residue on crockery. Take the racks out when you clean the filter and seals, and put everything back before the cycle.

Is it worth buying a dishwasher cleaner when vinegar is cheaper?

Both can work for light grease and smells, but a purpose-made cleaner is designed for grease and limescale together and is made for dishwasher parts, whereas frequent vinegar use can affect rubber seals. A cheaper compromise is citric acid for scale, a clean filter and a wiped seal. Check your manual, because some manufacturers recommend only specific products.