The short answer
On a Bosch dishwasher, dirty water left covering the filter most often comes down to a blocked filter and sump. Bosch dishwashers have no heated-dry element and no hard-food disposer: everything passes through a removable filter stack, which is the first thing to pull. The first check below needs no tools, and the list stops where a meter on live terminals begins.
What you observe
- Water stands in the bottom at the end of the cycle — The defining symptom, and it is a drain path question.
- The machine hums at the point it should drain — The pump is energised and moving nothing.
- Water backs up into the sink when it drains — The obstruction is outside the machine.
- NEAR MISS — water is on the floor rather than in the tub — That is a leak and a different page.
Causes, most likely first on a Bosch dishwasher
- Blocked filter and sump — Ranked first here: everything on this machine is caught by a filter rather than ground up, so a neglected filter starves the drain pump directly.
- Failed or obstructed drain pump — Ranked second: an obstructed impeller hums without moving water, and a failed one is silent.
- Kinked or blocked drain hose — Last on this list: the hose is flexible, it is behind the machine, and it is crushed every time the cabinet is pushed back.
Check in this order, and why
- Twist out the filter stack and clear the sump beneath — Glass chips and labels collect exactly there. First: likeliest cause, least effort.
- Listen for a hum at the moment the machine should drain — Hum without flow is a jammed impeller. Second: it separates the next two causes.
- Look behind the machine at the hose route — Any sharp fold is the fault. Third: only once the checks above are clean.
What an owner can safely check
- Bail the standing water out with a jug and a sponge — You cannot inspect a sump underwater.
Tools: jug, spongeAbout 15 min
- Remove the filter stack and clear the sump recess by hand — Wear a glove: broken glass ends up here.
Tools: glovesAbout 15 min
- Note exactly what you hear at the drain step and when — Silence and a hum point at different parts.
Tools: noneAbout 10 min
- Ease the machine forward and inspect the hose for kinks — Do not pull it out fully: the supply line is short.
Tools: torchAbout 15 min
- STOP HERE if the next step needs a meter on live terminals — That is where an owner check ends and a service call begins.
Before you open anything
Safety
Unplug the appliance or switch off its breaker before removing any panel. A capacitor can hold a charge after the power is off.
When to call a technician
Call once the filter, the spray arms and the drain path are all proven clear and the fault is unchanged, because the next tests are on live terminals inside a wet cabinet. Call immediately if you see water at the electrical panel, if the cabinet trips the breaker, or if there is standing water under the machine rather than in it.
Nearest pages of this class
What this page does not cover
This page covers Bosch dishwashers as a class, not one family or model line. It reasons from how Bosch builds this appliance — enough to rank the causes, not enough for wiring colours, torque figures or part numbers, which differ by family. A narrower page on this symptom is linked below; where it names your unit, start there.
Links: - [Bosch dishwasher that will not drain](/blog/bosch-dishwasher-drainage-failure-2)
Lead Appliance Repair Technician · 12 years experience
Experienced technician with 12 years specializing in washing machine and dryer repairs across all major brands.
