The E21 error on your Bosch Dishwasher means the machine has detected a problem with water draining out of the appliance. This usually points to a blockage somewhere in the drain system rather than a serious mechanical failure, so it's often fixable without calling an engineer.
| Error code | E21 |
|---|---|
| Meaning | Drain pump or drainage system fault — water is not clearing from the tub within the expected time |
| Severity | Medium — the dishwasher won't complete a cycle properly until it's resolved |
| Time to fix | 15–45 minutes |
| Tools needed | Bowl, cloth, gloves, and possibly a screwdriver |
What the E21 error means
The E21 code is triggered when the dishwasher's control board detects that dirty water is taking too long to drain away, or isn't draining at all. Bosch dishwashers monitor drain time as part of every cycle, and if the pump has to work too hard or too long to clear the water, the system flags it as a fault and stops the cycle to prevent damage.
In most cases this is caused by something physically blocking the flow of water rather than an electrical fault, which is why many homeowners can clear it themselves.
Common causes
- Food debris, glass fragments, or labels clogging the drain filter
- A kinked, blocked, or badly positioned drain hose
- Blockage in the kitchen sink air gap or garbage disposal connection
- A worn or jammed drain pump impeller
- Incorrect installation causing the hose to sit too high or too low
- Limescale or grease buildup restricting water flow over time
How to fix the E21 error
- Power down and check for standing water — Turn off the dishwasher at the wall and check how much water is sitting in the base of the tub.
- Clean the drain filter — Remove and rinse the filter assembly at the bottom of the dishwasher under running water to clear trapped food and debris.
- Inspect the drain hose — Pull the dishwasher out slightly and check the hose for kinks, tight bends, or blockages, straightening or clearing as needed.
- Check the sink connection — If the hose connects to a garbage disposal or air gap, make sure that connection point isn't clogged.
- Run a short cycle — Restart the dishwasher and run a rinse cycle to see if the water now drains properly and the error clears.
- Call a technician if it persists — If the error returns after cleaning the filter and hose, the drain pump itself may need replacing.
FAQ
Can I still use my dishwasher with an E21 error showing?
No, it's best to fix the drainage issue first, as running more cycles with standing water can cause bad odours and potential overflow.
Is E21 a sign the drain pump is broken?
Not always. Most E21 errors are caused by blockages in the filter or hose rather than a faulty pump, so check those first before assuming a part needs replacing.
How do I stop the E21 error coming back?
Clean the drain filter every few weeks and scrape large food scraps off plates before loading to reduce the chance of future blockages.
