The short answer
A dishwasher that will not drain is nearly always holding something it cannot pass — food debris, a blanking plug or a kinked hose. That puts a blocked filter or sump at the top of the list here and a jammed drain pump impeller at the bottom.
What owners actually report
- Water appears in the machine after the sink is used — Backflow from the disposer or a missing high loop in the drain hose.
- The pump hums but nothing moves — A drain pump running against a blockage or a jammed impeller.
- NEAR MISS — water on the floor rather than in the tub — That is a leak, and it belongs on the leak page.
What causes this, in order of likelihood here
- A blocked filter or sump — The filter catches what the spray arms wash off. Drainage is where water that the machine made on purpose goes wrong, so it leads whenever water is the complaint.
- The disposer knockout plug was never removed — On a new or newly connected disposer this blocks the dishwasher drain completely. It is an installation fault, not a failure. How the unit was put in is part of the machine, and a bad install follows it for its whole life.
- A kinked drain hose or a missing high loop — The hose has to rise before it falls, or the sink drains into the machine. It sits here because a blocked drain accounts for more water on a floor than every plumbing connection combined.
- A blocked air gap at the sink — The small chrome cylinder on the worktop blocks with debris and stops the drain dead.
- A jammed drain pump impeller — Glass, a fruit sticker or a bone fragment stops the impeller while the motor still hums.
Where to start, and what each check rules out
- Lift out the filter and look at what is under it — It comes out by hand and it answers the question in a minute.
- Ask whether a disposer was fitted recently — A new disposer with its knockout plug in place blocks the drain completely.
- Follow the drain hose for kinks and for a high loop — A hose crushed behind a cabinet or lying flat explains a slow drain on its own.
Step by step, as far as it is safe to go
- Bail out the standing water and remove the filter assembly — Wash it in hot soapy water and clear the sump underneath with a cloth.
Tools: cloth, cup
- Clean the air gap at the sink — Lift the cover, unscrew the cap and clear the debris inside it.
- Straighten the drain hose and restore the high loop — The hose must rise above the machine before it drops to the trap.
Tools: torch
- STOP before removing the drain pump or the sump housing — That means mains wiring and sharp debris inside a pump housing.
Power, panels and what not to do
Safety
Cut the power at the breaker before reaching into a sump — a drain pump can start under control even with the door open on some machines. Broken glass in a sump is the usual injury on this job, so use a cloth rather than bare fingers.
When this stops being a home repair
Filters, air gaps and hoses are owner work. A pump, a sump housing or a wiring fault is a service call, and a machine that fills from the sink needs a plumber rather than an appliance technician.
Nearest pages of this class
Generalized information — and what is missing from it
This page is generalized across Café dishwasher families and model lines. Wiring colours, torque figures and board part numbers are deliberately not here — they differ by family. A family- or model-specific page, where one exists, is linked below and is the more specific answer.
Links: - [Common Café Dishwasher Problems](/blog/caf-dishwasher-problems) - [Café Dishwasher: Abnormal Noise or Vibration](/blog/caf-dishwasher-abnormal-noise)
Lead Appliance Repair Technician · 12 years experience
Experienced technician with 12 years specializing in washing machine and dryer repairs across all major brands.
