The answer, before the detail
Expect kinked drain hose, or a lost high loop before anything else. Dishwashers collect what comes off the plates, and everything they collect ends up in the same few places — which is exactly why the ranking below looks the way it does.
The symptoms, and the ones that mean something else
- The cycle seems to run much longer than it used to — Machines that cannot drain often extend the cycle while they try again, so a long cycle can be the first sign.
- Water backs up into the sink when the machine drains — A shared waste line or a blocked sink trap, not a dishwasher fault at all.
- A humming sound during the drain phase with nothing leaving — The pump is being asked to run and cannot move water — a jam or a blockage downstream.
- NEAR MISS — the dishes are dirty but the machine drains fine — If the tub empties properly and the dishes are still poor, the cleaning page is the right one: spray arms and water temperature are the suspects there.
The ranking, and why it is this way round
- Kinked drain hose, or a lost high loop — Its rise-and-fall shape is not decorative: without it, the machine either cannot push water out or takes it straight back in, and both look identical from inside the tub. Number one here, because this is what the machine meets first and what owners notice last. A smaller brand rarely publishes a service manual to the public, so the order below leans on what is visible from outside rather than what a schematic would tell you.
- The filter stack packed with food debris — Modern machines use a fine filter stack rather than a hard-food disposer, which cleans better and blocks faster. Anything that will not dissolve — labels, seeds, bones, plastic film — ends up sitting on the mesh. It takes second place because the check is quick and because leaving it unchecked makes everything below it harder to read.
- A slow household drain backing up into the machine — It is on the list because owners rarely connect the two, and because a plumber and a technician are different calls: ruling this in before booking saves an entire wasted visit. It ranks third: real, but rare enough that chasing it first wastes an afternoon.
- An impeller stopped by something it swallowed — The drain pump sits under the sump and pushes water out through the hose. A small object that gets past the filter — a fragment of glass, a cherry stone, a plastic tag — can stop the impeller dead, and the pump then hums without moving anything. Least likely of the four, and the one that only makes sense once the others are ruled out.
What to check first, second, third
- Open the cupboard under the sink and follow the hose from the machine to the waste — Look for a kink, a crush point, and whether the hose rises before it drops. Start at this check: it is the one most likely to end the job on its own.
- Scoop the standing water out and look into the sump under the filter — Glass, labels and fruit stones collect there and go unnoticed while the filter is in place. Second, once the first check is clean.
- Fill and empty the sink beside the machine and watch how fast it clears — A slow or gurgling sink is a plumbing fault and it explains the dishwasher complaint entirely. Only worth doing once the two above are ruled out.
What you can do yourself
- Ease the machine forward enough to free a trapped hose — Do it slowly, with the door shut, and watch the supply line as you move it.
About 25 min
- Remove the filter stack, rinse it under a hot tap with a brush, and refit it locked home — A filter left a quarter turn short of home lets debris bypass it straight into the pump.
Tools: washing-up brush, clothAbout 20 min
- Run a hot flush through the sink waste before re-testing the machine — Grease that has narrowed a branch responds to hot water long before it needs a rod.
About 15 min
- STOP before testing anything electrical with the power on — The checks above are all done cold. A test that needs power applied is a technician test, whatever a video shows.
Before you open anything
Safety
Switch the dishwasher off at its socket or isolator before reaching into the sump or moving the machine — there is mains voltage inside the door panel and water in the tub, and the two only stay apart while the power is off. Wear a glove in the sump: broken glass collects there and it is not visible under standing water.
When this becomes a service call
The owner-side work ends at the sump opening. Anything that needs the machine pulled out, the pump housing opened or a circuit tested is a service call — and it is worth booking with the checks above already done, because that is what makes the visit short.
Nearest pages of this class
What is not on this page
Scope of this page: Kool Home dishwashers generally, not one family. Model-specific information — wiring colours, part numbers, resistance and torque figures — belongs on the page for that family, and where such a page exists it outranks this one.
Lead Appliance Repair Technician · 12 years experience
Experienced technician with 12 years specializing in washing machine and dryer repairs across all major brands.
