In short
Expect a sump filled with what came off the plates 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.
What you are seeing
- Nothing at all happens during the drain phase — complete silence — Silence where there should be a pump points at the electrical side rather than a blockage.
- An inch or so of water left in the bottom at the end of every cycle — The classic signature. A small amount of clean water in the sump is normal on some machines; a standing pool is not.
- Dirty water with food debris sitting in the tub — Debris in the water points at the filter and the sump rather than at the pump or the hose.
- NEAR MISS — water is escaping onto the floor — Water outside the machine is a leak, and that page comes first. Deal with the leak before the drainage complaint it may be causing.
What goes wrong here, in order
- A sump filled with what came off the plates — A dishwasher recirculates its water many times during a cycle, so the filter is doing its job constantly rather than once. It loads faster than owners expect and it is the first restriction water meets on the way out. It heads the list because it is the failure this class shows first, and the one an owner can settle without opening anything. This is a value-tier unit built to a price, which usually means fewer sensors and simpler controls: the mechanical causes rank above the electronic ones here.
- The sink waste spigot blocked with debris — A dishwasher that has never drained properly since a kitchen change almost always fails here. A machine that drained fine for years and then stopped is more likely to be blocked at that same spigot with grease. Second here: common enough to matter, and still answerable without a tool in your hand.
- A hose with no rise in it, so waste water siphons back — 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. Third in order, and the point where the checks start costing more time than they save.
- An impeller stopped by something it swallowed — It sits low on the list because everything above it is more common, cheaper and reachable — but it is the cause that most often needs a part. Bottom of the list — uncommon enough that starting here is how an afternoon disappears.
The order to check in
- Twist out the filter in the base of the tub and look at the mesh — A film you can see through is fine; a mat of debris is the fault, and it is visible the moment the filter is out. Start at this check: it is the one most likely to end the job on its own.
- If a disposer was fitted recently, confirm its dishwasher knockout was removed — The plug is inside the disposer inlet and is the single most common cause of a machine that never drained. Second, once the first check is clean.
- Feel along the hose where it passes behind the machine — A hose flattened between the cabinet and the back of the machine is hard to see and easy to feel. Third in sequence — useful, but rarely where the answer turns out to be.
Owner-side checks, in order
- Bail the standing water out, then clear the sump by hand — Use a jug and a cloth; wear a glove, because broken glass is common in a sump.
Tools: jug, cloth, gloveAbout 25 min
- Disconnect and clear the waste spigot, then refit with the clamp tight — Have a bowl and towels ready: the hose holds more water than expected.
Tools: screwdriver, bowl, towelsAbout 30 min
- Straighten the hose and secure the high loop up under the worktop — Use the clip the machine came with, or a cable tie to the cabinet wall.
Tools: cable tieAbout 20 min
- STOP if the fault is now down to a sealed or high-voltage part — Those need tools, training and a discharge procedure. Write down what you found and hand it over.
The part that is not optional
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 to call a technician
Call once the filter, the sump, the hose and the waste connection are clean and water still stands in the tub. Call immediately if the pump is silent when it should run: that is an electrical fault, and the next step is a meter rather than a cloth.
Nearby pages
What this page leaves out
This page is deliberately generalized across the Kostch dishwashers it covers. It does not carry model-specific wiring, torque values or component resistance figures — those belong on the page for your family, and that page takes precedence where it exists.
Lead Appliance Repair Technician · 12 years experience
Experienced technician with 12 years specializing in washing machine and dryer repairs across all major brands.
