A blocked dishwasher – or a dishwasher that can’t drain – is one of the most common and scummy dishwasher faults. And because the trusty dishwasher is such a cherished household appliance, we miss it when it’s out of action. As well as saving us the bother of rolling up our sleeves, it saves a lot of water. This guide will help you get your dishwasher unblocked ASAP and restore your dishwasher to its former glory.
How much water does a dishwasher use?
Glad you asked – it’s estimated that washing up by hand uses on average 49 litres of water, while the average dishwasher uses 10 to 12 litres.
Even by conservative estimates, this means you’re saving approximately 75% of the water used, making your dishwasher less of a luxury item and more of an eco-warrior in stainless steel. So let’s get yours fixed.
How do I know my dishwasher is blocked?
The first sign you might see that your dishwasher is blocked is a lot of standing water at the bottom. If it’s not draining at all, don’t worry; once you’ve found out the cause, you might then be able to fix it yourself.
What causes a blocked dishwasher?
Let’s look at the three main areas where a blockage is likely to form in a dishwasher, and how to unblock them.
Tools you may need:
- A shallow pan to catch drips
- Adjustable spanner
- Dishwashing detergent
- Clean dish-cloth
- Water spray
Safety reminder: Remember to switch off and unplug your dishwasher from your mains electricity before you start delving into and removing parts.
1. Blocked Filter
A dishwasher’s filter is its first line of defence against food bits and scraps coming in. Its job is to catch it before it has a chance to reach the pump and cause further problems. So your filter should be your first port of call when troubleshooting, and something you check and clean regularly to prevent blockages and further damage from happening.
How to fix a blocked dishwasher filter
Your dishwasher filter is very easy to check, clean or replace. You’ll find it at the bottom of your dishwasher. Depending on your particular make and model, remove it either by pulling or unscrewing it. If you’re not sure where your machine’s filter is located, check the manual or manufacturer’s website for details.
Give the filter a thorough clean:
- Rinse it under the hot water tap first
- If you’ve got a high-pressure setting on your kitchen tap, go at it with this
- Use an old toothbrush to scrub the mesh screen and plastic frame to remove any grease or particles stuck in the crevices
- Once it’s just like new, twist, lock or screw it back into place
If you use your dishwasher regularly, it’s a very good idea to clean your filters every week or so. Read our how to clean a dishwasher article for more on daily, weekly and monthly dishwasher maintenance that’ll keep your machine clean and serene for years.
2. Blocked spray arms
Your dishwasher spray arms on the motor spin around spraying hot water on your dishes when your dishwasher is doing its thing.
Just like the filter, the spray arms can get clogged up with bits of food and grime. The consequence of this is that the water jets become blocked so no water can get to your dishes, which means they won’t be coming out completely clean.
How to unblock your dishwasher spray arms
Again, this is a relatively simple task and can be done by following the steps below:
- With your appliance switched off and unplugged, remove both baskets
- Remove the centre bolt which holds the arms in place with an adjustable spanner
- Take the spray arms off the centre bolt
- Hold the spray arms under warm running water to remove any dirt and debris. You can also use some washing-up liquid and an old toothbrush. Use a toothpick to poke all the spray holes in each arm. You’ll be able to dislodge any bits of food this way.
- After the last rinse, reattach the spray arms
- Tighten the centre bolt with the spanner, add the trays back into your appliance and plug it back in. That’s it – it’s ready to use again.
Warning: Don’t use strong chemical cleaners on the sprayer arms. If the build-up isn’t removed during the first or second washing, soak the arms in hot water with a grease-cutting, dishwashing detergent for up to half an hour. Rinse and repeat until the build-up is gone.
The third possible cause of your blocked dishwasher is the drain. If your dishwasher drain is clogged, scummy water will collect in the bottom of the machine, along with food debris and potentially bacteria.
How to unblock your dishwasher drain
- This time, cut off the water supply to your dishwasher
- Unplug from your mains electricity
- First, check that the drain hose at the back of your dishwasher isn’t squashed or kinked – if it is, this could stop the waste water from draining away. If you’ve got a freestanding dishwasher, try to carefully pull it away from the wall to check there’s enough room for the hose to drain properly. If you’ve got an integrated dishwasher, this will be trickier and may be a job for a professional to help with
- If you’ve got a front kick plate, you may be able to do this yourself. Remove the front kick plate at the bottom of the machine. Some models have a door that allows access to the underside of the dishwasher. Use a screwdriver if there are screws to unscrew
- Slide a shallow pan under the bottom of the dishwasher, to catch any water that drips or leaks
- Find and remove the drain hose. The hose is white or transparent and it runs from the sink drain to the dishwasher drain pump. You might need to pinch a clamp to remove the hose or loosen a connector
- Once you’ve removed the hose from your dishwasher, you need to run some high-pressure water through it to remove any blockages. The best thing to do is to take it outside and use your garden hose with lots of pressure. Spray your garden hose into one end of your drain hose until the water comes out at the other end. If it doesn’t, there’s a major clog in there. You might have to squeeze the hose to help the blockage along. This will help to break down the clog until it flows out of the end (another reason why it’s a good job to do in your back garden). Take care as you squeeze, as you don’t want to split or damage the hose.
- Replace the drain hose and turn your water and electricity back on.
Is my drain hose connected to my waste disposal?
The drain hose from your dishwasher is usually plumbed to your kitchen sink waste or the drain of your kitchen waste disposal if you have one. If this is the case, you’ll want to keep your sink and disposal drain as clear as possible in order to allow water to freely pass through it. If your disposal is completely full and loosens up anything that needs a bit of help.
It would be ideal to also pour some baking soda and white vinegar down the drain, wait for a couple of minutes, and then follow with some boiling water.
How to avoid dishwasher blockages
While the above are some of the areas of your dishwasher that can easily become blocked and prevent the appliance from working to its full potential, these problems can be avoided by:
- Rinsing dishes before putting them in the dishwasher. Super simple because most standard dishwashers cannot cope with a build-up of food particles and this is commonly what causes clogs
- Doing a monthly service wash.
How to do a monthly service wash on your dishwasher
A monthly service wash involves putting your dishwasher on a full cycle while it’s empty, with just a little bit of white vinegar and baking soda poured in. This will remove small particles of dirt and grime that have the potential to build up and cause blockages, ensuring your appliance continues to run at peak performance for longer.
Also, take the time to regularly check the three areas mentioned above, check out our how to clean a dishwasher article and you’ll keep on having crystal clean glasses, plates, pots and pans.
How do you clear a clogged dishwasher?
Identify and then clear the source of the blockage:
- Sprayer arms
- Drain hose
You can take out the filter and sprayer arms and clean them in the sink. If your blockage is in the drain hose you will need to safely remove it and unclog it.
Can you put a drain unblocker in a dishwasher?
No. Drain unblockers contain extremely strong chemicals that should only be used in emergencies, in drains, when you have exhausted all other, less harmful methods of unblocking a drain. If you use it in your dishwasher, it may leave behind chemical residues that are harmful to your health.
What causes the water not to drain from a dishwasher?
It’s usually a blockage in the filter, the sprayer arms or the drain hose. You need to locate and clear the blockage by cleaning and unclogging each item.
How do I know if my dishwasher drain pump is bad?
If you’ve checked and cleared your dishwasher filter, sprayer arms and drain hose and your dishwasher is still not draining, you could have a faulty drain pump. In this case, it’s time to call an expert.