The short answer
This machine is moved, which means its drain arrangement is rebuilt from scratch every time it is used. Ranked first on this platform: The drain hose height at the sink. The checks below follow that ranking, and the first of them need no tools and no panel removed.
What you observe
- Behaviour changes depending on where the machine is standing — A fault that moves with the machine is about the installation, not the machine.
- It has not drained properly since the machine or the kitchen was worked on — A fault dated to a building job belongs to the building job.
- Standing water above the filter at the end of every cycle — Water sitting on top of the filter names the blockage.
- NEAR MISS — it drains but leaves dishes dirty — That is a wash-performance question and it is diagnosed from the filter and the arms rather than from the drain.
Causes, most likely first on this platform
- The drain hose height at the sink — A portable machine drains over a sink edge, so the height it hangs at decides everything: too high and the pump cannot lift the water, too low and the machine siphons itself empty as it fills. It ranks first on this platform because the drain hose hooks over the sink edge rather than joining a waste trap, so its height is set by wherever the machine happens to be standing that day — and that height alone decides whether it drains or siphons back.
- A kinked drain hose or a missing high loop — The drain hose has to rise above the level of the tub and then fall, or the machine cannot hold what it has pumped. It ranks second here because the machine is moved, which means every hose and every connection is disturbed regularly rather than fitted once.
- A blocked filter and sump — Everything the machine washes off ends up in the sump, and the filter is what holds it there. Ranked third: worth checking once the causes above have come back clean.
- Something jammed in the pump — Glass, a fruit stone or a bone fragment reaching the impeller stops it dead. The pump hums and moves nothing, and repeating the attempt only heats the motor. It ranks fourth rather than higher: real on this platform, and less common than the causes above it.
Check in this order, and why
- Look at where the hose end sits relative to the machine — It is the variable unique to this class of machine. It leads because it tests the top-ranked cause.
- Pull the machine out, or look under the sink, and follow the hose along its whole run — A crush or a sag is visible at once. Tests the second-ranked cause.
- Lift the filter out and look into the sump below it — Free, immediate, and it is the leading cause. Tests the third-ranked cause.
What an owner can safely check
- Hook the hose over the sink edge at the height the instructions give and secure it — Secure it: a hose that falls into the bowl siphons.
Tools: cable tieAbout 15 min
- Straighten the hose and secure the high loop up under the worktop — Use the clip it came with, or a tie to the cabinet wall.
Tools: cable tieAbout 20 min
- STOP at the first panel that needs a tool, and write up what you found — A technician who arrives knowing which checks came back clean spends the visit fixing rather than repeating them.
Before you open anything
Safety
Unplug the machine or switch off its breaker before removing any panel, and close the supply valve before disturbing a fitting. Broken glass in a sump is common: wear a glove and look before you reach.
When to call a technician
Call when the filter, the hose and the household drain are all clear and the machine still will not empty, because what is left is the pump or the control.
Nearest pages of this class
What this page does not cover
This page is written for the MST dishwasher as a class, not for one family or one model line. Where a family- or model-specific page exists for your unit, that page is the more specific answer and the one to read first. Deliberately not here: part numbers, wiring colours and disassembly order, which differ by family.
Lead Appliance Repair Technician · 12 years experience
Experienced technician with 12 years specializing in washing machine and dryer repairs across all major brands.
