The short answer
F18 on this washing machine means the drainage hose is blocked or kinked — that is what the manufacturer published for it, and no more. Do not run another programme: the machine cannot get rid of the water it already has. One of the checks below is an owner check, and the rest of the work is behind a panel.
Error codes
Reference| Code | Meaning |
|---|---|
| F18 | The drainage hose is blocked or kinked. |
What the machine does alongside the code
- The pump runs on without the level dropping — The machine is trying to drain against a restriction.
What triggers F18, most likely first
- A kink where the hose passes behind the machine — It goes first because it is the commonest and it needs no tools: the hose folds against the wall when the machine is pushed back, and a bend that looks gentle from the front can be closed at the back.
- A blocked house drain or standpipe — It ranks here because the appliance is then working perfectly and reporting the building, which is why the check belongs before any part is bought.
- A failing drain pump — Last of the likely causes: a pump that is worn moves water slowly, but the four cheaper causes above produce the identical code and have to be cleared first.
Check in this order, and why
- Pour a jug of water into the standpipe — A standpipe that backs up on a jug will certainly back up on a full machine.
- Listen for the pump during the drain phase — A pump you can hear turns the problem into a restriction; silence points at the pump or its circuit.
- Clear and inspect the filter or trap — This is both a check and a fix, and it is the one part of the drain path that is designed to be opened by the owner.
- Body: Decide whether the pump is running before anything else — a running pump and a silent pump send you to opposite ends of the same path.
The reset, then the owner-safe checks
- Test the drain point with a jug of water — A standpipe that backs up on a jug will certainly back up on a full appliance.
Tools: jugAbout 5 min
- Straighten the hose over its whole run and test the standpipe with a jug of water — Check the outlet height as well: a hose looped too high cannot drain however clear it is.
Tools: jugAbout 20 min
- Run a short cycle and watch the drain phase to the end — You are looking for whether the level falls at all, and how fast, not just whether the code returns.
About 45 min
- STOP HERE if the path is clear and it still will not empty — The pump and its valve sit inside the machine, behind a panel and next to standing water.
Before anything is opened
Safety
Unplug the machine or switch off its breaker before any panel comes off — a capacitor can hold a charge after the power is off. Close the supply tap before touching a hose, expect standing water when a filter comes out, and never work round the door interlock.
When this is a service call rather than a reset
Call straight away if water is leaking onto the floor, if the appliance is silent through the drain phase, or if it fills and never empties.
Neighbouring codes on Bosch washing machines
What this page does not cover
This reading applies to the Bosch washing machine line as a whole, not to one family or model. It does not cover what differs between model lines — wiring colours, connector positions, part numbers and service-mode sequences — which are in your own model manual and which a technician matches to the rating plate rather than to this code. Where a family- or model-specific page for this code exists, it is linked from the code index below and it is the more specific answer.
Links: - [Bosch washing machine error codes](/blog/bosch-washer-error-codes)
Where to go next
Lead Appliance Repair Technician · 12 years experience
Experienced technician with 12 years specializing in washing machine and dryer repairs across all major brands.
