The E21 error on your Bosch Dishwasher means the drain pump or drain path has a fault that is stopping water from leaving the machine properly. In most cases a blocked filter, drain hose, or pump impeller is the reason, and clearing the blockage resolves the fault.
| Error code | E21 |
|---|---|
| Meaning | Drain pump fault or restricted drainage flow |
| Severity | Medium — the dishwasher will not complete a cycle until fixed |
| Time to fix | 15–40 minutes |
| Tools needed | Towel, bowl, screwdriver, multimeter (optional) |
What the E21 error means
E21 is triggered when the dishwasher's control board detects that water is not draining fast enough, or that the drain pump is drawing too much or too little current. This is usually a mechanical blockage rather than an electronic failure. The good news is that most E21 faults can be cleared without calling an engineer, since the cause is almost always debris in the filter, hose, or pump housing.
Common causes
- Food debris or a broken glass fragment blocking the drain filter
- A kinked, crushed, or blocked drain hose behind the machine
- Debris jammed in the drain pump impeller
- A blocked or faulty non-return valve where the hose connects to the sink drain or waste disposal
- A worn or failing drain pump motor
- Incorrect installation height of the drain hose causing water to siphon back
How to fix the E21 error
- Turn off and unplug the dishwasher — Always disconnect power before checking any internal parts for safety.
- Remove and clean the filter assembly — Take out the lower basket, twist and lift the filter, then rinse it under running water to clear trapped food and grease.
- Check the drain pump for obstructions — Look into the filter housing recess for the pump impeller and remove any glass, bones, or plastic fragments by hand.
- Inspect the drain hose — Pull the dishwasher forward, check the hose for kinks or blockages, and straighten or clear it as needed.
- Check the sink connection point — If the hose connects to a sink waste or garbage disposal, make sure the knockout plug was removed and the connection isn't clogged.
- Run a short cycle to test — Plug the dishwasher back in and run a quick rinse cycle to confirm the E21 code has cleared and water drains fully.
FAQ
Can I run the dishwasher again after clearing E21?
Yes, once the filter and drain path are clear, run a short cycle to confirm the error doesn't return before loading a full wash.
Is E21 dangerous to ignore?
It won't damage the machine immediately, but standing water can cause bad odours and eventually strain the pump motor, so it's best fixed promptly.
Do I need an engineer for this repair?
Most E21 cases are DIY-fixable by cleaning the filter and hose. If the pump itself has failed, a replacement part and professional fitting may be needed.
