Why Your Dishwasher Isn’t Draining and What You Can Do

Why Your Dishwasher Isn’t Draining and What You Can Do

---

If after the dishwashing cycle you detect water left inside, you have got a classic dishwasher not draining problem.

To tell the truth, this is, perhaps one of the most common dishwasher problems. For example, when we get a request for Miele dishwasher repair in London, in half of the cases it is a problem we discuss here.

The good news is that most such issues you can fix even without any complicated dishwasher repair tips.

But let’s discuss this in detail.

---

Quick Symptoms & Safety Checks

Before contacting a repair company, whether it is for domestic dishwasher repair or commercial dishwasher repair, we recommend a quick assessment and safety checks.

Quick Symptoms: Standing water vs. slow drain

When you detect water in the dishwashing tub, evaluate its amount. It may give you a quick key to what’s happened to your appliance.
​
Typically, there can be two cases:

• Water standing to an inch or more – pump failure or control board issues
• Just a small puddle –clogged filter or drain hose

Safety Checks: Switch off power and water

If it is a clog, you can tackle the issue without any preparation. In all the other cases, you need to prepare your appliance for the necessary procedures.
​
For this, first, turn off the water supply valve to ensure no water input. Second, unplug the unit from the socket to de-energise it to make it fully safe and ready for further fixes.

---

Most Common Causes

Now, let’s dive deeper into the common dishwasher problems that cause the issue. For example, when we get a request for Hobart dishwasher repair with complaints about poor draining, it is typically one of the following three causes.

Clogged filter or sump

This is where the problem arises first.

The filter task is to prevent food debris from getting inside the system. Over time, the filter becomes clogged and stops letting water drain out of the machine.
​
If some very fine particles escape the filter, they get into the sump. For example, on one of our last SIEMENS dishwasher service call-outs, we detected a critical sludge at the bottom of the sump. Over time, the sump may accumulate a large amount of such particles. In turn, such a clog results in preventing water from flowing out.
​

Blocked/kinked drain hose or air gap

This is the second issue that leads to poor draining.

Typically, a clog in these components results from oils, fats, and fine powder-like particles that get into the system. For example, after cooling, oils and fats turn into sludge that envelop the inner side of the hose and get accumulated in the gap. So, the problem may occur even with a clean filter.​

When the clog becomes critical, water will not find enough space to go through, and issues with draining arise.
​

Faulty drain pump or impeller

This is a serious problem. For example, a few of our Bosch dishwasher repair call-outs were about a malfunctioning drain pump or a jammed impeller and it took time to repair without replacing. 

​To clarify, water gets out of the dishwasher not because of gravity but due to the efforts of the drain pump. Over time, it can fail and stop working, which leads to the dishwasher not draining.

To go further, the drain pump consists of the impeller, a fan-like part that physically moves the water. If a toothpick or glass pieces slip through the filter and get into the system, they may jam the impeller, which stops its running.

---

Step-by-Step DIY Checks

Here are some dishwasher repair tips to follow when your dishwasher is not draining.

Clean the filter & sump

It is the easiest task. Just follow the steps:

1. Locate the filter, the cylindrical item with a flat mesh piece
   
2. Twist the filter left and remove it
   
3. Put the parts in water and clean with a soft brush to remove sludge
   
4. Wipe out the sump and get rid of the sludge there
   
5. Place the filter back in its location and twist right to reassemble
   

Inspect and flush the drain hose

This is a more complicated task. So, to do it yourself, you need some basic knowledge of dishwasher installation and de-installation. To clarify, the drain hose is located on the side or back of the dishwasher. Therefore, to deal with it, you need access to this side or back. In other words, you need to pull your appliance from under the counter. If you aren’t sure you can do this, turn to professionals.

The DIY steps are as follows:

1. Unplug your dishwasher to de-energise it
2. Access the appliance side or back
3. Locate the drain hose
4. Check it at its entire length for kinks
5. Arrange a pallet and sufficient cleaning cloth to deal with residual water
6. Disconnect the hose (at its both sides)
7. Flush the hose to get rid of blockages
8. Connect the hose back as it was
9. Plug in the appliance

Run a rinse/drain cycle & check error codes

If you detect a significant amount of water, do a quick DIY check that may help you identify the issue.

Run a quick washing cycle or drain-only cycle if your model has one. Listen carefully to the coming sounds:

• A humming sound – the impeller is jammed or the pump has failed
• No sound at all – the pump isn't getting power or is completely dead

​In any of these cases, we recommend turning to an engineer and describing the signs you detected. If your dishwasher flashes with an error code, remember the code and inform your engineer about it.

---

When to Call an Engineer

Unless you are a professional engineer fully familiar with the dishwasher’s engineering in general and your model one in particular, your only DIY options include troubleshooting minor clogging and checking for error codes. For all other cases, it is recommended to turn to a professional.

In short, the cases when to call an engineer, cover:

• Deep and severe clogging
• Professional drain hose flushing
• Any pump failures
• Control board failure

Burning smell, tripped breaker, repeated errors

If you are facing repeated errors even after cleaning the filter and flushing the hose, it means the issue is somewhere else, and you need a professional to detect and fix it.

Burning smells or a tripped breaker is one of the most dangerous issues for your safety:

• A burning smell indicates a serious electrical fault
• The tripped breaker indicates a short circuit in the pump or wiring

​So, if you notice them, stop using the dishwasher and contact an engineer without delay.

---

Prevention & Maintenance Checklist

While there are many causes for a dishwasher not draining, you can prevent most of them. Here is a brief prevention and maintenance checklist:

• Scrape plates before loading
• Clean the filter every 30-40 cycles
• Protect the machine control board from surge with a dedicated a surge protector 
• Keep the control panel clean and dry
• De-energise the unit to reset it and clear temporary glitches from the control board's memory

---

Need help? Book a dishwasher engineer in London

At LE Company, we are happy to help you if your dishwasher is not draining or encounters any other issues. Just contact us at +44 203 603 7172 or send your request online on our Contact page. We cover all areas in London.