E18 on a Bosch appliance means water is not moving the way the machine expects. Which end of the water path is at fault depends on which machine you are standing in front of — and that is the whole point of this page.
E18 appears on 9 jobs in our records: six on Bosch washers, three on Bosch dishwashers. We handle 55 Bosch washer jobs and 369 Bosch dishwasher jobs.
On a Bosch washer: the drain pump
Six of the nine, and they describe themselves almost identically.
"It seems to be having trouble draining water, and often gives the E:18 error."
"Error code: E18, water pump might be broken."
"The washer keeps getting E18 errors and is unable to drain water properly. Not sure if some blockage is inside the machine."
The tech's finding where we have it: "Drain pump needs to be replaced."
One model dominates: the WAP24200UC. It appears on three separate jobs in our records — including two different customers describing the trouble in nearly the same words, and one where the tenant reported it rather than the owner.
That is Bosch's compact 24-inch front-loader, the one that goes into flats and closets where a full-size machine will not fit. Like LG's combos, these units have a tight drain path and they run constantly.
If you have one and it is throwing E18, the drain pump is the first thing to look at — and if the machine is more than a few years old, the pump rather than a blockage is the likelier answer.
On a Bosch dishwasher: a supply fault
Three of the nine, and the notes read completely differently.
"E18 water supply fault."
"Thermador dishwasher, error code E18. Water supply error, is not draining."
"Error message — Fault E18 — Water Supply."
Note that middle one: a water supply error on a machine that "is not draining". That is not a contradiction in the customer's description — it is how these faults present. The machine cannot establish the water movement it expects, and the control reports it from the supply side.
The parts in our dishwasher E18 records are on the supply side of the machine — a water valve and its regeneration valve.
One of these three was a Thermador, which is Bosch-built and uses the same codes.
Why this matters before you order a part
Here is the practical takeaway, and it is the reason this page covers two appliances instead of one:
Search "Bosch E18" and you will get answers for both machines mixed together. Someone with a dishwasher reads washer advice and starts looking at the drain pump; someone with a washer reads dishwasher advice and starts checking taps and inlet screens. Both waste an afternoon.
So, plainly:
- Bosch washer, E18 → look at the drain: pump, filter, hose, standpipe. Expect the pump.
- Bosch dishwasher, E18 → look at the supply side first: taps, inlet hose, Aquastop valve, inlet screens.
Confirm which you have before you buy anything.
What you can safely check — Bosch washer
- Open the lower access panel, put a tray under the drain tube, and let the water out.
- Pull and clear the pump filter behind the same panel. Coins, clips and lint felt live there.
- Check the drain hose is not kinked and not pushed too far into the standpipe, and that it rises before it falls.
- Run a drain-and-spin. If it empties and E18 stays away, that was the fault.
- Listen during the drain. Buzzing or grinding with nothing moving means the pump, not a blockage.
What you can safely check — Bosch dishwasher
- Check the supply tap under the sink is fully open.
- Check the inlet hose is not kinked where it runs behind the machine.
- Check the Aquastop, if your model has one — the thickened section at the tap end of the hose. If its safety valve has tripped, the machine gets no water at all.
- Clean the inlet screen at the tap end of the hose, with the water off.
- Clear the filter and sump in the floor of the tub anyway, since the notes on our jobs mention draining too.
Call a tech when the code survives those checks, or when a Bosch washer's pump makes noise without moving water.
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Related pages
- Bosch Dishwasher E24 Error — the Bosch drain code we see most
- Bosch Dishwasher E25 Error — the drain pump blocked
- Washer Won't Drain — the symptom, all brands
- Bosch Dryer F:03 Error — the condensate pump on Bosch's compact dryers
- Bosch Appliance Repair — every Bosch appliance we service
Frequently asked questions
What does E18 mean on a Bosch washer? It is a drain fault. The machine cannot clear the water in the time it expects, so it stops. On our jobs the finding was that the drain pump needed replacing, though a blocked filter or kinked hose produces the same code.
What does E18 mean on a Bosch dishwasher? Our dishwasher records describe it as a water supply fault — the machine cannot establish the water movement it expects. Start at the supply: the tap, the inlet hose, the Aquastop valve and the inlet screen.
Why does the same code mean different things on two Bosch machines? Because the code numbering is per appliance line, not shared across the brand. The digits are the same and the family of fault — water not moving — is similar, but the component involved sits at opposite ends of the water path. It is worth confirming which machine you are reading about before ordering a part.
My Bosch WAP24200UC keeps showing E18 — is that a known problem? It is the model we see it on most. The WAP24200UC appears on three separate E18 jobs in our records. It is Bosch's compact 24-inch front-loader, with a tighter drain path than a full-size machine, and the drain pump is the usual answer.
What parts have you fitted for a Bosch E18? On the washers, the drain pump. On the dishwashers, parts from the supply side — a water valve and its regeneration valve. Which ones fit depends on the model, so they should be matched to the rating plate rather than ordered on the code alone.
My Thermador dishwasher shows E18 — same thing? Yes. Thermador dishwashers are built by Bosch and use the same codes; one of our three dishwasher E18 jobs was a Thermador.