The grey tank is the first suspect
Many Dometic laundry appliances are washer-dryer combination units, and those do drain - into the vehicle grey tank. A drainage complaint on this equipment is therefore usually a full grey tank or a closed dump valve rather than anything inside the machine.
What you are seeing
- Water remains in the drum at the end of a cycle.
- The machine drains slowly and the cycle stalls.
- The grey tank monitor reads full.
- Water backs up into a shower tray or a sink when the machine drains.
- Drainage got worse over several days without dumping.
- Not this fault: Water on the floor with an empty drum is a leak - read that page.
- Not this fault: A vented dryer with no wash function has no drain at all.
Most likely causes, in Dometic order
- Grey tank full — Why ranked: First on this equipment. It is the most common cause by a wide margin and it needs no tools to check.
- Dump valve closed, or the tank not vented — Why ranked: Second: a closed valve or a blocked vent stops the tank taking anything, and the machine backs up.
- Drain hose kinked or routed badly in a tight cabinet — Why ranked: Third. Space is very limited and hoses are crushed when the machine is refitted.
- Pump filter blocked with lint and debris — Why ranked: Fourth. Compact filters block quickly, and vehicle laundry catches a lot of grit.
- Drain pump failed — Why ranked: Last, and identified by a silent drain step with a clear filter, an open valve and an empty tank.
What to check, in order
- Check the grey tank level and the dump valve position. — Because: This is the leading cause and it is settled in a moment.
- Note whether water backs up into the shower or a sink when the machine drains. — Because: That is the tank rather than the machine, and it affects everything on the same drain.
- Ease the machine forward and check the drain hose for kinks. — Because: Tight cabinets crush hoses whenever the machine is refitted.
- Listen for the pump during the drain step. — Because: A silent pump with everything else clear points at the pump itself.
Checks you can do safely
- Check the grey tank level and dump it if it is full. — N: 1 — Tools: None — Time: moderate
- Confirm the dump valve is fully closed for normal use and the tank is vented. — N: 2 — Tools: None — Time: quick
- Ease the machine forward and inspect the drain hose route. — N: 3 — Tools: Torch, second person — Time: moderate
- Check the pump filter with the machine switched off and a tray ready. — N: 4 — Tools: Tray, cloth — Time: moderate
- Run a short cycle and listen for the pump at the drain step. — N: 5 — Tools: None — Time: one cycle
Before you open anything
Safety
Unplug the appliance or switch off its breaker before removing any panel. A capacitor can hold a charge after the power is off. A pump filter holds water - open it with a tray and towels ready and never with the machine powered. Follow the site rules for grey tank disposal. Never open a pump filter on a machine full of water. Do not dump a tank anywhere but at a proper disposal point. Dry any spill in a vehicle immediately; a wet floor in a small space is a fall risk.
When this becomes a service call
The machine will not drain with an empty tank and a clear filter. The pump is silent during the drain step. Water backs up into the shower or a sink with an empty tank. There is a burning smell from the pump area.
What this page does not cover
This is generalized information for Dometic laundry appliances as a group. It does not separate vented dryers, which have no drain, from washer-dryer combination units that drain to a grey tank, and it names no model-specific pump or filter. Where a family- or model-specific page exists it supersedes 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.
