The short answer
On the COSDWV family the usual reason a Cosmo dishwasher is leaving water in the bottom is disposer or shared branch blocked, and that is where the order below departs from the brand-generic article one level up: on the disposer-connected build it outranks air gap or a disposer knockout still in place. The check that confirms which build you have is simple — look under the sink: a drain hose entering the side of a food disposer means the machine drains through it. The filter, the hose, the air gap and the disposer inlet are owner work; the pump under the sump is not.
What you observe on these models
- The sink drains slowly as well — A shared blockage downstream, which is plumbing rather than appliance.
- Water with debris floating in it — A filter that has stopped holding anything back.
- The tub empties and then refills — Siphoning back, which is the loop or the non-return valve.
- It started right after a new disposer was fitted — The knockout plug, until proven otherwise.
- Standing water in the sump at the end of every cycle — The defining symptom, and it says nothing yet about where the blockage is.
- NEAR MISS — water on the floor rather than in the tub — That is a leak, and the leak page is the one to read instead.
Causes, most likely first on the COSDWV family
- Disposer or shared branch blocked — Ranked first here: it ranks first on a disposer-connected machine because the shared branch is the part of the system the machine has no control over.
- Air gap or a disposer knockout still in place — Second: it ranks high on a disposer-connected machine because a new disposer is the single most common trigger for a machine that has never drained since.
- Drain pump impeller jammed — Third: it ranks here because the sound is diagnostic: a hum with no water movement is a jam, and silence is usually something upstream of the pump.
- Drain hose kinked behind the machine — Fourth: the hose is soft and the machine gets pushed back against it, usually by whoever last cleaned the floor. A kink stops drainage completely without breaking anything.
- Filter and sump packed with debris — Fifth: the pump can only move what reaches it. A filter matted with paper labels, seeds and fat leaves standing water in a machine whose pump is perfectly healthy.
- Non-return valve stuck — Sixth: it is placed low because it is less common than everything above and sits in the same area as the pump.
Check in this order, and why
- Run the sink and see whether it drains freely — A slow sink and a wet dishwasher share one blockage.
- Lift the air-gap cover on the worktop and clear it — A small chamber that silts up quietly and stops the flow completely.
- Listen at the end of a cycle for a hum with no water moving — A hum means the pump is powered and jammed rather than dead.
- Pull the machine forward and follow the hose — A kink behind the cabinet stops drainage without anything being broken.
Before you open anything
Safety
Power off at the spur, water off at the valve, then open anything. Those two come first because the wiring and the plumbing in this cabinet run alongside each other. Leave the door latch alone: defeating it lets a hot cycle run with the door open. Bail the water out before you tip the machine forward, and treat anything in the sump as sharp until you have seen it.
Models in the COSDWV family
Reference| Model number | Family key |
|---|---|
| COS-DWV24TTR | cosmo:dishwasher:cosdwv |
When to call a technician
Bring someone in once the free checks are clean, and sooner if the sink drains slowly too — that is a plumbing job rather than an appliance one, and a drain engineer will fix it faster than an appliance technician.
Other pages for this family and brand
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