The short answer
On the BlitzHome BH dishwashers specifically, this fault sits one level below the brand-generic answer: the models in this family share a layout, and that layout changes which check comes first. A small amount of water in the sump is normal. A tub with standing water above the filter is not. If the machine was recently installed, the disposer knockout plug is the first thing to check, not the last.
What you observe on these models
- Standing water covering the filter at the end of a cycle — The classic presentation — the cycle ran and nothing left.
- Dirty water appears in the sink when the dishwasher drains — The shared waste line is restricted rather than the machine.
- The problem started right after the machine was installed — An installation fault rather than a wear fault — the knockout plug is the classic one.
- NEAR MISS — the machine never filled — An empty tub at the end of a cycle is a fill problem.
Causes, most likely first on this family
- Disposer knockout plug never removed — Second: when a dishwasher is plumbed into a new waste disposer, a moulded plug inside the disposer inlet must be knocked out first, and it is forgotten constantly.
- Filter and sump blocked with food debris — Ranked first because clearing it resolves both the drainage complaint and the smell that usually comes with it.
- Drain pump failed or not being commanded — Last, and it is reached by elimination rather than by inspection.
- The departure from the page above this one — The generic article lists these causes in frequency order across every model the brand sells. Here the ordering also accounts for how this family is built — which panel comes off first, and which component is behind it — and that pushes the accessible causes up.
Check in this order, and why
- Listen during the drain step — A hum with no level change means obstruction. Complete silence means the pump is not being run, which is a different branch.
- Check the air gap fitting on the worktop if there is one — Lift the cover and look for debris. A blocked air gap stops drainage completely and is often the last place anyone looks.
- Look for the high loop in the drain hose — The hose must rise above the level of the tub before falling to the waste, or the machine siphons and never finishes.
- What this family's layout decides — The construction of these models determines what can be confirmed quickly and what cannot, and the order above follows that directly. It is not a generic checklist reordered; it is the sequence that this platform actually rewards.
Before you open anything
Safety
Switch the machine off at its isolating switch and close the supply valve before reaching past the tub. A built-in dishwasher carries mains wiring in a wet enclosure, and the two share a very small space behind the kickplate.
When to call a technician
Call once the filter, the spray arms, the seal, the settings and the connections under the sink have all been checked and the fault survives them. Call at once if water is reaching the cabinet base or the floor, because a built-in machine hides its leak until damage is done.
Other faults covered for this family
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Experienced technician with 12 years specializing in washing machine and dryer repairs across all major brands.
