The short version
A WQP dishwasher that will not drain is usually reporting a restriction somewhere between its own sump and the household waste connection. Each of the four places that restriction lives is checkable in order, and only the last of them needs a technician.
The observable signs on this platform
- The drain pump runs and the water does not move — The path downstream of the pump is blocked. Hose, air gap or household connection, in that order.
- A hum then silence at the drain step — The pump is trying and failing to turn, which points at a jammed impeller or a failing motor rather than a blockage.
- Water backing up into the sink when the machine drains — Shared waste plumbing rather than the appliance. The blockage is in the household drain and the dishwasher is only reporting it.
- NEAR MISS — the cycle never reaches the drain step — A machine that stops partway through, or never starts, is a cycle or control fault.
Causes, most likely first on the WQP family
- Filter and sump loaded with debris — First on this family. Everything that leaves the dishes has to pass the filter, and once it is loaded the drain path narrows from its very first inch.
- Drain hose kinked, crushed or looped wrongly — Second. The hose must rise to a high point before it falls, and a hose crushed behind the machine after a push-back, or one that lost its high loop during an installation, will not drain reliably.
- Waste-disposal knockout plug still in place, or the household connection blocked — Third, and the one people never think of. A new disposal ships with a plug that must be removed before a dishwasher is connected to it, and a blocked air gap or standpipe produces the same result.
- Drain pump impeller jammed by glass, a seed or a label — Fourth. The pump is usually healthy and simply obstructed, which is why replacing it often fixes a problem that clearing it would also have fixed.
The order to work in, and the reason for it
- 1. Bail the standing water out and pull the filter and sump cover — You cannot diagnose through standing water, and the debris you find is itself the evidence.
- 2. Start a cycle, advance to the drain step and listen — A running pump with no water movement means a downstream blockage; a hum-and-stop or a silence means the pump or its control.
- 3. Pull the machine out and follow the drain hose — Look for a crush point, a lost high loop and a kink at the cabinet penetration.
Safety first
Safety
Unplug the appliance or switch off its breaker before removing any panel. A capacitor can hold a charge after the power is off. Assume there is broken glass in the sump of any dishwasher with a drainage complaint — use a cloth and a torch rather than bare fingers, and bail rather than reach.
Models in the WQP family — The model numbers this page covers.
Reference| Model number | Family key |
|---|---|
| WQP12-77E1B-US | bertazzoni:dishwasher:wqp |
| WQP8-7740-US | bertazzoni:dishwasher:wqp |
When to call a technician
Call when the filter and sump are clear, the hose is sound with its high loop intact, the household connection is open, and the pump still will not move water. That combination points at the pump or the control that drives it, and both need the machine out and the lower access open. Call sooner if water backs into the sink, since that is household plumbing rather than the appliance and is a different trade.
Other problems covered for the WQP family
Lead Appliance Repair Technician · 12 years experience
Experienced technician with 12 years specializing in washing machine and dryer repairs across all major brands.
