Dishwasher
E18
The E18 error code on a Bosch dishwasher means the machine can’t drain water fast enough — or at all. It’s one of the more common Bosch faults, and in most cases you can fix it yourself without calling an engineer.
What does this error mean?
E18 is Bosch’s drainage error, triggered when the dishwasher detects that water hasn’t cleared from the base within the expected time during a wash cycle. The control board monitors drainage progress and throws E18 when it times out. This usually points to a blockage or restriction somewhere in the drainage path, rather than a broken pump.
Est. repair cost
£0 DIY (filter clean) | £15–£30 DIY drain pump part | £80–£150 professional repair
🔍 Likely causes
🛠️ Step-by-step fix
Switch off the dishwasher and unplug it from the mains. Use a jug and towels to remove any standing water from the base of the tub.
Remove and clean the drain filter: twist it anticlockwise to unlock, lift it out, and rinse it under the tap, scrubbing away any grease or food debris with an old toothbrush.
Check the sump area (the recess under the filter) for large food debris — remove anything you can see by hand.
Inspect the drain hose at the back of the machine. Check it isn’t kinked, crushed, or blocked. Disconnect it from the sink waste or standpipe and blow through it to confirm it’s clear.
Run your kitchen sink to confirm it drains freely — a slow sink can cause a Bosch dishwasher to show E18 due to backpressure. If the sink is slow, unblock that first.
Reassemble everything, plug the machine back in, and run a short rinse programme to see if the error clears. If E18 returns immediately, the drain pump itself is likely faulty.
📞 When to call a professional
If the filter, hose, and sink are all clear but E18 persists, the drain pump is most likely seized or burnt out — this requires a professional repair. Call a Bosch-approved or Which?-trusted appliance engineer and tell them: ‘My Bosch dishwasher is showing E18, I’ve cleaned the filter and checked the hose, so I suspect the drain pump.’ This gives the engineer a head start and may reduce call-out time.
⚖️ Repair or replace?
A drain pump replacement typically costs £80–£150 for parts and labour in the UK. If your dishwasher is under 5 years old, repair is almost always worth it. If it’s 8 years or older and has had previous faults, a new mid-range Bosch dishwasher starts at around £400–£500, and the investment is often better value than repeated repairs.