The answer, before the detail
A Black+Decker BCD dishwasher that leaves water behind is telling you the path out is blocked somewhere along its length. The path has four parts — sump, hose, air gap or disposer connection, and pump — and only the last needs a technician. This page works along the path in order, because that is the order that finds it fastest. What separates BCD units here is visible without a tool: a filter that twists out of the tub floor, or nothing of the sort on the other build.
What the owner actually sees
- A pool covering the tub floor when you open the door — Enough to scoop rather than a film in the sump recess.
- Water backing up into the sink when the machine drains — A disposer fitted recently is the first thing to suspect here.
- Stale water odour on opening — Water that is not leaving is water that is standing, and standing water in a warm tub smells.
- It drains, but slowly and not completely — A restriction rather than a blockage — more typical of the hose route than of the sump.
- NEAR MISS — a film of water always in the sump recess — That is normal on most machines; it keeps the seal wet. It is not a drainage fault.
Most likely first on this family
- The filter and sump are blocked — On a grinder build it drops down the list, which is why establishing the build comes first. Labels, seeds and broken glass all end up here.
- The drain hose is kinked, blocked or has lost its high loop — It ranks high because it is common, invisible and free to fix. A hose that has to be lifted to drain has lost its loop.
- The disposer knockout plug or the air gap is blocking the outlet — This is the top cause on a machine that has never drained since it was fitted, and it is not a fault at all — it is a plug that was never removed. A new installation that has never drained points here before anywhere else.
- The drain pump is jammed or has failed — Last, because every cause above it is reachable without tools and this one is not. A hum with no drain, after the filter and hose are clear, is what is left.
Check in this order, and why
- Scoop the water out and look at the sump — You cannot inspect a drain path through four inches of water, and the water tells you something first: clean or dirty.
- Lift the filter and check underneath — A torch makes the difference between looking and seeing.
- Follow the drain hose under the sink — Second because it is the next part of the same path.
- Inspect where the hose joins the waste — An air gap comes apart by hand and blocks with the same debris as the filter.
Power off first
Safety
Switch the machine off at its breaker before reaching behind the kick plate or the door panel — water and mains wiring share the same small space in a dishwasher, and a capacitor can hold a charge after the power is off. Leave the door latch and its switch exactly as they are: the machine is meant to stop the moment the door opens. Broken glass in the sump is a hand injury waiting to happen; use a torch and a cloth, never bare fingers.
Where the owner job ends
The condition is how far along the drain path the blockage is. Sump, filter, hose and waste connection are all owner work and account for most standing water. The pump, the check valve and the wiring under the tub are not, and a machine that trips its breaker when it tries to drain should be switched off and booked.
Other faults covered for the BCD models
Lead Appliance Repair Technician · 12 years experience
Experienced technician with 12 years specializing in washing machine and dryer repairs across all major brands.
