Stop using it for now. Carrying on with this fault risks further damage or a leak. Switch it off at the wall until it has been looked at.

What F18 actually means

The machine has tried to pump the water out, failed to get rid of it in the expected time, and stopped with the drum still full.

F18 is a drain fault on Bosch (and the related Neff and Siemens machines). The control board watches for the water level to drop once the drain pump runs; when it doesn't, the cycle is halted and the code shown, usually leaving standing water in the drum and a wash that won't spin. It covers the whole drain route \u2014 pump filter, sump hose, pump itself and the waste pipe under the sink.

What usually causes it

Blocked pump filter \u2014 coins, hair clips, screws, buttons
Blocked or kinked waste hose, or a blocked sink spigot/washing machine trap
Something jammed in the pump or sump hose stopping the impeller
Damaged pump impeller, so it spins but shifts no water
Failed drain pump needing replacement

What you can safely check yourself

Work through these in order. Anything beyond this — panels off, testing parts, anything to do with the wiring — is an engineer's job, and not one to attempt with the machine plugged in.

Turn the machine off at the wall for a minute, then power back up \u2014 sometimes it will re-attempt the drain.
Clean the pump filter behind the flap at the bottom front. Have a shallow tray and towels ready, as water will come out.
Check the waste hose isn't kinked, crushed behind the machine or pushed too far down the standpipe.
If the waste connects to the sink trap, check that spigot isn't blocked \u2014 they silt up with grease, and if a blanking crosshair was never cut out of the fitting the machine will never drain properly.
Use the emergency drain/door release if your model has one to get the water and washing out before anything else.

When to call someone

This sometimes clears with the checks above. If it comes back, it needs looking at properly. We cover Nottinghamshire, Derbyshire and Leicestershire, and it's £66 including VAT for an engineer to come out and diagnose it — £84 in total if it's repaired on the visit with no parts needed. Any parts needed are quoted on site before we fit them — you decide. Every repair carries a 90-day workmanship guarantee.

Outside our area? The explanation above still stands — take it to a local engineer and tell them the code. Knowing it saves them time and you money.

Bosch F18 error — washing machine

What F18 actually means

What usually causes it

What you can safely check yourself

When to call someone

Other Bosch washing machine codes

Need it looked at properly?