How to unblock a dishwasher that won't drain

How do I know my dishwasher is blocked?

A blocked dishwasher gives itself away long before it stops working altogether. Any one of these is worth a filter check:

• Water is left standing in the bottom of the tub when the cycle ends


• The dishwasher drains slowly, or dirty water backs up into the kitchen sink


• You hear gurgling, thumping or a shaking noise while it is running


• Dishes come out gritty, filmy or still dirty


• The dishwasher smells stale, even straight after a hot cycle


• The programme stalls part-way through and the display stops counting down

Beko names the same signs on its own support pages: gurgling, thumping or shaking while the machine runs "is an indication that there is a blockage in your appliance". Bosch puts it more bluntly still: if the pump is blocked, "waste water cannot be pumped out of the appliance".

One thing that is not a fault: a little residual water in the recess under the filter. Bosch's own pump-clearing instructions assume you will find some there and tell you to sponge it out. It is a tub full of dirty water that points at a blockage.

Before you start: power off, gloves on

You are about to put your hands into a wet electrical appliance, so take two minutes over this.

• Switch it off and unplug it. Beko's instruction is exactly that: "Turn off the power supply to the dishwasher and unplug it." If the socket sits behind the machine, isolate it at the fused spur instead.


• Wear gloves. Bosch is emphatic about this, because "broken glass fragments can collect" in the pump area.


• Get your kit together first: old towels, a shallow tray, a sponge, a mug or ladle, a soft brush, a cocktail stick and a hand screwdriver. Bosch warns that where a pump cover needs unscrewing you should use a manual screwdriver and "never use an electric one".


• Stop if the electrics have tripped. If the dishwasher trips the RCD, or you can see water near the socket, that is a job for an electrician or an appliance engineer.

Step 1: Bail out the standing water

Nothing else works properly with a tub full of water, and the moment you pull the filter out the water finds the floor. Take the bottom basket out, scoop the water into a bucket with a mug or ladle, then finish the last inch with a sponge. That is Bosch's own method: soak the water up with a soft sponge and "gradually ladle it out of the appliance". Keep a towel under the door as you work.

Step 2: Clean the filter and the sump

The filter catches the food that washes off your plates so it does not end up back on the clean ones, or in the pump. It sits in the sump, the shallow recess in the floor of the tub that funnels water to the drain pump. This is where the problem is most of the time, and it is the one part every manufacturer expects an owner to clean.

• Find it and lift it out. It is in the floor of the tub, under the bottom basket: a cylinder with a flat mesh plate around it. Bosch describes removal as unscrewing the filter cylinder at the base and lifting the unit out. Beko's locks clockwise, so it comes out the other way. If it will not budge, check your manual rather than forcing it.


• Separate the parts. Most come apart into a coarse filter and a fine or micro filter, and food gets trapped between the two.


• Rinse both under a running tap. Bosch: "Clean both filters under running tap water. You can use a small brush to gently clean the inside of the filter and remove smaller pieces of debris. Do not use anything abrasive as this can damage the filter." A torn filter mesh lets debris straight into the pump, which is a much bigger job.


• Clear the sump underneath. Sponge out anything left, then look. Labels off jars, olive stones, fruit stickers, cherry tomato skins and chips of glass all end up here. Wear gloves and lift them out.


• Refit it and lock it. This step is the one people get wrong. The coarse filter seats into the micro filter, and then twists home: Bosch says twist it "until both arrows line up", Beko says clockwise "until it clicks". A filter dropped in loose lets food bypass it completely and blocks the pump instead.

Run a short hot programme with the machine empty. If the water drains away, you are done, and the fix from here is simply to clean the filter more often.

Step 3: Unclog the drain pump and impeller

The drain pump sits directly under the filter and pushes waste water out through the hose. Its impeller is a small plastic paddle wheel, and it only takes a fruit stone, a bottle cap or a shard of glass to jam it. Bosch publishes the homeowner procedure, and it is worth following exactly:

• With the filter out and the water sponged away, put your gloves on. Bosch: "it is essential that you use protective gloves when placing your fingers in the pump area".


• Prise off the pump cover. Bosch's own trick is to use a teaspoon, then "grip the cover by the lug and pull it upwards until it resists" and pull it forwards. Some models need a hand screwdriver instead.


• Check for foreign objects and remove any deposits, feeling around the whole cavity.


• Turn the impeller with a finger. Bosch's test is to "ensure that the pump impeller can move freely". If it is stiff, something is still wedged in. If it spins but a vane is snapped off, the pump needs replacing.


• Refit the cover until it clicks, then put the filter back and lock it, and refit the basket.

Bosch is clear about the limit of this job too: "In some cases the impeller can also break. We would then recommend booking an engineer, who will be able to replace the faulty part."

Step 4: Unblock the dishwasher drain hose

If the filter and pump are clear and the tub still holds water, the drain hose is next. This is also where a dishwasher that has never drained properly since the day it was fitted usually turns out to have an installation problem rather than a blockage.

Start with the height, because it is free to check and it is easy to get wrong. Beko's published requirement for its dishwashers is that the drain hose connection should be "a minimum of 50cm and a maximum of 100cm above the floor to work correctly". Too low and the machine siphons itself empty and refills with waste water. Too high and the pump cannot push water over the top. Check the figure in your own manual, because it varies by brand.

Then work through the hose itself:

• Unplug the dishwasher and turn off the water supply. The isolating valve is usually under the sink; if you cannot find one, use the main stopcock.


• Pull the machine forward. Beko's instruction is to carefully pull the dishwasher forward so you can reach the drain hose. An integrated machine may need releasing from the worktop first.


• Look for crushing and kinks. Beko: check "that the drain hose has not been crushed, kinked or twisted or is blocked". The classic is a hose pinched flat between the back of the machine and the wall, or trapped under a foot when the dishwasher was pushed back into its gap.


• Check the length. Beko warns not to exceed the maximum length quoted in your manual. A long extension added by an installer makes the pump work against far more water than it was designed for.


• Disconnect and flush it. Put a tray and towels under the connection at the machine end, release the clip and let the trapped water out. Then release the end that joins the waste under the sink, take the hose outside and run water through it. A garden hose at mains pressure is usually enough to shift a grease plug.


• Refit both ends with the clips properly seated, restore the water and power, and run a short cycle while you watch for leaks.

Step 5: Check the sink waste it drains into

A dishwasher does not have its own drain. Its hose joins the waste under the kitchen sink, so the dishwasher can only empty as fast as that pipe allows.

The tell is easy. Fill the sink, pull the plug and watch. If the sink also drains slowly, or gurgles, the blockage is in the kitchen waste and cleaning the dishwasher filter will never fix it. Kitchen wastes block with cooled fat and food fines, the same grease the dishwasher has been pumping into them.

Our guide to unblocking a kitchen sink covers clearing the trap and the waste pipe properly. Clear that first, then retest the dishwasher.

Do dishwasher unblockers and drain cleaners work?

Short answer: not for this. Neither Bosch's nor Beko's published drainage procedure uses a chemical unblocker at any step. Both fix a blocked dishwasher mechanically, by clearing the filter, the pump and the hose.

That is down to what the blockage actually is. A chip of glass, an olive stone or a jar label jammed in an impeller does not dissolve, and a caustic unblocker just sits against the seals, the plastic impeller and the hose until the pump that is not working manages to shift it.

There are two chemical products manufacturers do endorse, and neither one is an unblocker:

• A dishwasher descaler. Bosch recommends descaling periodically, and more often in a hard water area, where limescale narrows everything over time.


• A vinegar solution, for spray arms only. Bosch suggests soaking the spray arms in a vinegar solution to dissolve food particles blocking the outlet nozzles, then washing them in soapy water afterwards.

Clogged spray arms: dirty dishes, not drainage

Blocked spray arms will not stop a dishwasher draining, but they are the usual reason dishes come out dirty, and people often find them while chasing a blockage. Bosch's procedure:

• Unscrew and detach the upper spray arm, then unclip the lower one and lift it away.


• Clear the small outlet nozzles with a cocktail stick.


• Soak the arms in a vinegar solution to dissolve what is stuck, then wash them in soapy water and rinse thoroughly.


• Shake the water out, twist the upper arm's clip back into position and press the lower arm down until it clips.

Then check the arms spin freely by hand. A tall dish or a fallen fork stopping the arm turning is a two-second fix people spend a whole afternoon hunting for.

When to stop and call an appliance engineer

Stop and get someone out if any of these apply:

• The filter, pump and hose are all clear and the tub still fills with water. The drain pump itself is the likely fault, and Bosch's advice at that point is to book an engineer to replace the part.


• The impeller is broken, or a vane has snapped off.


• The dishwasher trips the electrics, or water is getting anywhere near the socket.


• It is leaking onto the floor as well as failing to drain.


• You would rather not pull an integrated machine out from under a worktop. Beko's own line is that it does not recommend attempting an appliance repair yourself.

How to stop your dishwasher clogging again

• Scrape, do not rinse. Bosch: "Before loading dishes into the dishwasher, always ensure that all food debris is scraped off beforehand. If this is not done, the debris can build up and possibly block the filter, spray arms and pump." Scraping the solids off is enough; rinsing every plate under the tap wastes water.


• Check the filter weekly. That is Beko's published interval: clean the filters weekly, or whenever they become clogged. It takes under a minute once you have done it twice.


• Deep clean every few months. Beko suggests a thorough clean every few months to keep limescale, bacteria and odours down. Wipe the door seals with a damp cloth, without pulling them away from the metal.


• Descale periodically. Bosch recommends it, and more often in a hard water area.


• Lock the filter back in every time. Food bypassing a loose filter goes straight to the pump, which is the repair you were trying to avoid.


• Mind the hose when the machine moves. After pulling the dishwasher out, check the drain hose is not trapped or kinked before you push it back.

Blocked dishwasher FAQs

Why is there water in the bottom of my dishwasher after every cycle?

Because the waste water is not getting out. Check in order: filter, then drain pump and impeller, then the drain hose, then the sink waste the hose joins. A blocked filter is the most common cause and the easiest to fix. If all four are clear, the drain pump has failed and needs replacing by an engineer. A small amount of residual water in the recess under the filter is normal.

How do I unclog a dishwasher drain hose?

Unplug the machine, turn off the water and pull it forward, then check the hose for crushing, kinks and twists, because that costs nothing. If it looks fine, drain it into a tray at the pump end, release it from the sink waste and flush it through outside. Step 4 above has the full method.

How high should a dishwasher drain hose be?

Beko's published requirement is a minimum of 50cm and a maximum of 100cm above the floor. Below that the machine can siphon its own water out; above it the pump struggles to lift the water. Every manufacturer sets its own figure, so check your manual. If your hose runs along the floor or up over a tall unit, that alone can be why it will not drain.

Can I use a drain unblocker or bleach to unclog a dishwasher?

It will not clear a mechanical blockage, and neither Bosch nor Beko uses a chemical at any step of its published drainage fix. Glass chips, olive stones and jar labels do not dissolve, and a caustic unblocker sits against the seals and the impeller until the failed pump manages to shift it. The chemicals manufacturers do recommend are a dishwasher descaler, used periodically, and a vinegar solution for soaking blocked spray arms.

Why does my dishwasher drain into the sink?

The waste hose joins the same pipe as the kitchen sink, so when that pipe blocks the water backs up into the lowest opening. Fill the sink and pull the plug: if it drains slowly or gurgles, the fault is in the kitchen waste, not the dishwasher.

Is a blocked dishwasher covered by appliance cover?

Not the unblocking itself. Clearing a blockage or cleaning a filter is routine maintenance, which appliance cover excludes (cover plan terms and conditions, p.21 §8.2(d)). A mechanical or electrical breakdown is different: Smart Plan's appliance module covers parts and labour up to £225 per appliance in a 12-month period, so a failed drain pump on a covered dishwasher is the kind of repair it is there for. Three things worth knowing before you sign up: a £95 call-out fee applies in the first 30 days, cover is modular so you only add the appliances you want covered, and once you use a service a 12-month agreement period begins. The full detail is on our appliance cover page.

More appliance help

• Washing machine stops mid-cycle: the same filter-and-pump logic on a different machine


• How to unblock a kitchen sink: clear the waste your dishwasher drains into


• Appliance repair: book an engineer for a failed drain pump


• Appliance help and cover: guides and cover for the rest of the kitchen

Manufacturer sources used on this page: Bosch UK, dishwasher not draining, Bosch UK, cleaning a dishwasher filter, Bosch UK, cleaning dishwasher spray arms and Beko UK, what to do when a dishwasher did not drain. Always check your own appliance manual first, because figures vary by model.