Dishwasher Not Draining? 7 Troubleshooting Tips to Try First

A dishwasher full of standing water is the last thing you want after a wash cycle. When your dishwasher isn’t draining, it leaves dirty water sitting at the bottom – a messy, unhygienic hassle. Before you panic or call for repairs, remember that many drainage problems have simple causes you can fix yourself.

In this guide, we’ll cover seven common reasons for a dishwasher not draining and how you can troubleshoot each one. These easy tips might save you an expensive repair call. We’ll also point out when an issue is likely beyond a quick fix and needs professional attention. (If you’re in Wirral, the experts at Grange Electrical are ready to help if it comes to that.)

Let's get your dishwasher draining properly again with these first-step solutions.

1. Dirty or Clogged Filters

Why this causes drainage problems: Modern dishwashers have filters at the bottom to catch food particles and prevent them from clogging the drain pump. If these filters become clogged with bits of food, grease, or debris, water can't flow out freely. A blocked filter is one of the most common reasons for a dishwasher not draining.

How to check and clean the filters:

• Turn off power: Safety first – unplug the dishwasher or switch it off at the wall. Ensure no cycle is running.

• Remove the bottom rack & find the filter: Pull out the lower dish rack to expose the dishwasher floor. Locate the filter (usually a cylindrical or mesh screen around the base of the spray arm) and remove it (most filters twist out or lift up).

• Clean the filter: Rinse the filter under warm running water. Use a soft brush or old toothbrush to gently scrub away grease and food debris. Make sure to clear out all the little holes or mesh.

• Check the filter well (sump): With the filter out, wipe around the area it sits in. Remove any gunk or stray bits of food you find in the sump (wear gloves in case there are sharp fragments like broken glass).

• Reinstall the filter: Put the filter back in place, ensuring it locks in properly. An improperly seated filter could allow debris into the pump or reduce drainage efficiency.

After cleaning the filters, run a short wash or rinse cycle and see if the dishwasher drains. This simple cleaning often solves the issue. If cleaning the filter doesn’t get your dishwasher draining, the problem might lie deeper in the system. Also, if the filter is damaged or stuck and you can’t clean it properly, you may need to replace it or have a professional take a look.

(Tip: Clean your dishwasher’s filter about once a month to prevent clogs.)

2. Blocked Drain Hose

Why this causes drainage problems: The drain hose carries waste water from your dishwasher to the sink drain. If this hose becomes clogged with food debris, grease, or soap residue, water can’t flow out and will back up into the dishwasher.

How to clear the drain hose:

• Check the sink connection: Make sure your kitchen sink drain is clear. If you have a waste disposal unit (garbage disposal), run it to ensure it's empty. A clogged sink or disposal can prevent the dishwasher from draining.

• Find the dishwasher hose: Look under the sink for the thick hose coming from your dishwasher. Place a bucket or large bowl underneath its connection point. If you suspect a blockage, you can disconnect the hose from the sink drain to inspect it (do this only if you feel confident).

• Inspect and clear the hose: Loosen the clamp and detach the hose from the sink drain pipe. Check the inside of the hose for clogs. Use a long flexible brush or a piece of wire (like a straightened coat hanger) to gently clear any gunk inside. You can also flush water through the hose to help push out the blockage. Be careful not to puncture the hose.

• Reconnect and test: Reattach the hose to the sink drain and tighten the clamp. Ensure it’s on firmly to avoid leaks. Then run a short dishwasher cycle to see if it now drains properly.

If the dishwasher still doesn’t drain, the blockage might be further along the line, or you may not have fully cleared it. If you’re not comfortable doing these steps or the problem persists, it’s time to call a professional appliance repair service.

(Note: To avoid drain hose clogs in the future, scrape off large food scraps before running the dishwasher, and occasionally run an empty hot cycle with a dishwasher cleaner to clear grease build-up.)

3. Kinked or Improperly Installed Hose

Why this causes drainage problems: Even if your drain hose isn’t clogged, its positioning matters. If the hose is bent sharply (kinked) or squashed, water can’t flow through it properly. Additionally, if the hose was not installed with a proper 'high loop' (an upward arch) or is set at the wrong height, it may cause water to remain in the dishwasher or even flow back into it.

How to fix hose positioning issues:

• Check for kinks: Unplug the dishwasher and pull it out slightly. Check the hose behind the machine and under the sink for any kinks or squashed sections. Straighten the hose and ensure nothing (like items in the cupboard) is pressing on it.

• Add a high loop: Ensure the drain hose has a 'high loop' under the sink. This means the hose goes up to a point higher than the dishwasher’s base (usually attached to the underside of the worktop) before dropping down to the drain. The high loop prevents backflow of water. This usually ensures the hose is at a proper height. Just make sure the hose end isn’t too low (which can cause siphoning) or too high (which makes the pump’s job harder).

After adjusting the hose, push the dishwasher back into place carefully (so you don’t kink it again). Then test a wash cycle. A properly positioned hose allows water to drain quickly when the pump runs. If it still doesn’t drain properly after these fixes, the cause might be something else – possibly a faulty pump – that needs professional attention.

4. Food Blockages in the Pump or Spray Arms

Why this causes drainage problems: Small bits of debris can sometimes bypass the filter and get stuck in the dishwasher’s drain pump or other internal parts. Pieces of broken glass, seeds, bones, or labels can jam the pump’s impeller (the little blade that pushes water out), preventing water from draining. Blocked spray arm holes usually won’t stop draining, but they indicate debris in the system that could also clog the pump.

How to clear internal blockages:

• Power off and access the sump: Turn off the dishwasher and remove the bottom rack. Take out the filter (as in Tip 1) to get to the sump (the small well where water pools under the filter). Use a torch (flashlight) to look for debris down there.

• Remove any debris: With gloves on, carefully pick out any visible gunk, food bits, or foreign objects. You might find bits of soft food, broken glass, or even small utensils or plastic fragments. Even a tiny shard can block the pump, so remove everything you see.

• Clean the spray arms: Check the spray arms for clogs too. If spray holes are blocked, remove the arms (they usually twist or clip off) and rinse them under running water. Use a toothpick or thin wire to poke out any debris in the holes.

• Reassemble and test: Put the filter and spray arms back in place. Then run a short cycle and see if the dishwasher now drains properly.

Often, clearing these internal blockages will solve your draining problem. If you suspect something is still stuck in the pump that you can’t reach (for example, you hear a loud hum and water still isn’t draining), it's time to call a professional. They can safely take apart the pump and remove the obstruction.

5. Faulty Drain Pump

Why this causes drainage problems: The drain pump is the part that forces water out of the dishwasher. If this pump fails or its motor doesn’t run, the dishwasher won’t be able to empty water, no matter how clear the filters or hoses are. Pumps can fail due to wear and tear, electrical faults, or damage from foreign objects.

How to tell if the pump is faulty:

• You’ve tried the fixes above (the filters and hose are clear), but water still won’t drain.

• When the dishwasher should be draining, you hear either nothing or just a faint humming noise, and the water stays put.

• Some models may show a blinking light or error code indicating a drain/pump issue.

What to do: There’s no easy DIY fix for a failed drain pump – it will need repair or replacement by a professional. Avoid running the dishwasher until it’s fixed (otherwise it will just fill with more water that can’t be pumped out).

Call a professional technician: Replacing a dishwasher pump is a complex task involving electrical connections and seals. It’s best handled by a qualified appliance repair engineer who can confirm the pump is faulty and install a new one safely.

If you’re in Wirral, you can contact Grange Electrical’s appliance repair service for prompt help with a faulty pump. Professional repair will have your dishwasher draining properly again without the stress of tackling it on your own.

6. Air Gap Issues (Where Applicable)

Why this causes drainage problems: An air gap is a small fitting (often a little cylindrical cap mounted on your sink) that prevents dirty water from siphoning back into the dishwasher. Not all kitchens have this device. If you do, a clogged air gap can block the dishwasher’s drain water from flowing out properly.

How to fix an air gap clog:

• Check for an air gap device: Look for a small cap or vent on your sink (usually near the taps). If you don’t see one, your dishwasher likely doesn’t have a separate air gap (it might use a high loop in the hose instead), so you can skip this tip.

• Clean the air gap: If you do have an air gap, remove its cap (it might twist off). You’ll see a plastic chamber underneath. Clear out any debris, food particles, or gunk inside. Use a small brush or a toothpick to dislodge anything stuck, and rinse it with water.

• Check the connected hose: Under the sink, find the hose coming down from the air gap (leading to the drain). Make sure this short hose isn’t clogged or kinked. Straighten it if needed.

• Reassemble and test: Put the cap back on the air gap. Now run the dishwasher and watch when it drains. If the air gap was the issue, you should no longer see water spilling from it; the water will go down the sink drain normally.

If your kitchen doesn’t have an air gap, or cleaning it didn’t resolve the problem, then the cause of the dishwasher not draining lies elsewhere (such as the drain hose or pump). You may need to troubleshoot those or call a professional.

7. Electrical or Sensor Faults

Why this causes drainage problems: If you've ruled out clogs and other mechanical issues, the remaining culprit might be an electrical or sensor fault inside the dishwasher. Modern dishwashers use sensors (like a float switch that detects water level) and electronic controls to manage each cycle. If a sensor malfunctions or the control board fails to signal the drain pump, the dishwasher might not drain even though nothing is physically blocking it.

How to address possible electrical issues:

• Reset and door latch: Sometimes the dishwasher just needs a reboot. Turn it off for a minute and then back on to clear minor glitches. Also, make sure the door closes snugly and latches, because if the machine thinks the door is open, it may not start the drain cycle.

• Inspect the float switch: The float is a small device in the dishwasher’s base that rises with the water level. If it’s stuck (for example, grime could be keeping it in the up position), it might prevent the dishwasher from running correctly. Clean around the float and ensure it can move up and down freely.

If these steps don’t help and the dishwasher still won’t drain, then you’re likely dealing with a faulty electrical component or sensor that requires professional diagnosis. At this point, calling a qualified repair service is the best move. Grange Electrical’s appliance repair team in Wirral can test the internal parts, find the exact issue, and fix it safely, so you don’t have to troubleshoot any further.

Keep Your Dishwasher Draining

Most dishwasher drainage problems come down to blockages or installation issues that are usually simple to fix. By cleaning the filter, clearing clogs from the drain hose, and making sure the hose is properly positioned (with no kinks and a high loop), you can solve the majority of cases where a dishwasher isn’t draining. Regular maintenance – like scraping off excess food from dishes and cleaning the filter monthly – will also help prevent many drainage issues.

That said, if you’ve tried these troubleshooting tips and your dishwasher still won’t drain, there may be a more serious fault (such as a failed pump or an electrical glitch). At that point, it’s wise not to push the machine any further. Instead, call a professional. Grange Electrical’s appliance repair services in Wirral are ready to help with expert diagnosis and repair. A skilled engineer can quickly find the cause of the problem and get your dishwasher back to draining properly. With the right help, that standing water in your dishwasher will be a thing of the past, and you can get back to hassle-free kitchen clean-up.