The short answer
On a Cove dishwasher that has been in service for years, a drain complaint usually means accumulation rather than an installation error: grease and scale narrowing the drain hose, filtration that a rinse no longer clears, and a check valve that has had a long life. The good news is that on a machine of this quality these are all repairable rather than terminal.
What you are actually seeing
- Draining has become slower over months rather than failing suddenly — Means: on-page
- Cleaning the filter helps for a few cycles and then the pool returns — Means: on-page
- The drain sounds different, where the machine used to be near-silent — Means: on-page
- A greasy film is visible around the filter housing — Means: on-page
- The tub partly refills after it has drained — Means: on-page
- The cycle stops early with a full tub — Means: different-fault — Go to: cove-dishwasher-cycle-fault
- Water on the floor rather than in the tub — Means: different-fault — Go to: cove-dishwasher-water-leak
- Body: Match what you see before you take anything apart. Draining has become slower over months rather than failing suddenly. Cleaning the filter helps for a few cycles and then the pool returns. The drain sounds different, where the machine used to be near-silent. A greasy film is visible around the filter housing. The tub partly refills after it has drained. Some near-miss symptoms belong on a different page: The cycle stops early with a full tub points at a cycle fault, covered on cove-dishwasher-cycle-fault; Water on the floor rather than in the tub points at a leak, covered on cove-dishwasher-water-leak.
Causes, ranked for this machine
- Grease and scale narrowing the drain hose and sump over years — Why this rank: First on an older machine because the loss is gradual, which matches a symptom that has crept up rather than appeared overnight
- Filtration that is blinded rather than blocked, so rinsing no longer clears it — Why this rank: Fine filtration can look clean and still be closed up by grease, which is why a soak tells you more than a rinse
- A check valve holding partly open and letting water back into the tub — Why this rank: Explains a tub that drains and then partly refills, which reads as a failure to drain at all
- A drain pump losing performance rather than failing outright — Why this rank: On a quiet machine this shows as a changed sound rather than a laboured one
- A drain hose disturbed by later kitchen work — Why this rank: Still worth checking, but it ranks lower on a machine that drained correctly for years
- Body: Ranked for a premium built-in dishwasher: hard-plumbed, on a dedicated supply, installed under a worktop by a fitter, quiet by design, with hand-cleaned filtration and a condensation dry that depends on rinse aid. Most likely: Grease and scale narrowing the drain hose and sump over years. First on an older machine because the loss is gradual, which matches a symptom that has crept up rather than appeared overnight. Next most likely: Filtration that is blinded rather than blocked, so rinsing no longer clears it. Fine filtration can look clean and still be closed up by grease, which is why a soak tells you more than a rinse. Third: A check valve holding partly open and letting water back into the tub. Explains a tub that drains and then partly refills, which reads as a failure to drain at all. Fourth: A drain pump losing performance rather than failing outright. On a quiet machine this shows as a changed sound rather than a laboured one. Fifth: A drain hose disturbed by later kitchen work. Still worth checking, but it ranks lower on a machine that drained correctly for years.
What to check, in order
- Soak the filtration rather than rinsing it, and judge how long the improvement lasts
- Run a hot cycle with a dishwasher cleaner to strip grease from the hose and sump
- Check whether the tub refills after draining, which points at the check valve
- Listen at the machine during the drain and compare it against how it used to sound
- Body: Each check rules out the causes above it. First, soak the filtration rather than rinsing it, and judge how long the improvement lasts. Second, run a hot cycle with a dishwasher cleaner to strip grease from the hose and sump. Third, check whether the tub refills after draining, which points at the check valve. Fourth, listen at the machine during the drain and compare it against how it used to sound.
Checks you can safely make yourself
- Switch off at the breaker, remove the full filter assembly and soak it in hot water with detergent before scrubbing and holding it to the light — Tools: bowl, brush, gloves — Time estimate: half an hour plus a soak
- Run the hottest cycle with a proprietary dishwasher cleaner and an empty machine, then check whether draining improves — Tools: dishwasher cleaner — Time estimate: one long cycle
- Drain the machine, wait, and check whether water has returned to the sump — Tools: torch — Time estimate: half an hour
- Listen at the door during the drain step and note whether the sound has changed from what you remember — Tools: notepad — Time estimate: one cycle
- Check the drain hose height in the adjacent cabinet and restore the high loop if it has sagged — Tools: cable tie — Time estimate: a quarter of an hour
- Body: Checks an owner can make with the machine switched off at the breaker, or by watching a cycle. Step one: Switch off at the breaker, remove the full filter assembly and soak it in hot water with detergent before scrubbing and holding it to the light. Tools: bowl, brush, gloves. Time: half an hour plus a soak. Step two: Run the hottest cycle with a proprietary dishwasher cleaner and an empty machine, then check whether draining improves. Tools: dishwasher cleaner. Time: one long cycle. Step three: Drain the machine, wait, and check whether water has returned to the sump. Tools: torch. Time: half an hour. Step four: Listen at the door during the drain step and note whether the sound has changed from what you remember. Tools: notepad. Time: one cycle. Step five: Check the drain hose height in the adjacent cabinet and restore the high loop if it has sagged. Tools: cable tie. Time: a quarter of an hour.
Safety first
Safety
Switch off at the breaker before bailing the tub or reaching into the sump, and wear gloves: broken glass in the sump is the most common injury on this job. Never run a disposer with a hand near it. On a machine of this age, remember that the door carries a custom panel under spring tension set years ago: do not loosen door hardware, and treat any water reaching fitted cabinetry as urgent rather than cosmetic. Unplug the appliance or switch off its breaker before removing any panel. A capacitor can hold a charge after the power is off. unplug-before-service
Where the owner fix ends
On an older machine, call a technician once the filtration is genuinely clear, a cleaner cycle has run and draining is still slow. A check valve or a drain pump on a machine of this quality is a worthwhile repair rather than a reason to replace, and the cabinetry work of fitting a new integrated machine usually exceeds the part.
Nearest pages of the same kind
Generalized information
This page is generalized across the Cove dishwasher line. Fully integrated machines carrying a custom cabinet panel and machines with a finished front share the ranking above but not every part, and this page does not cover a specific model, control revision or installation. Family- and model-specific pages, where they exist, are linked below.
Links: - [Common COVE Dishwasher Problems](/blog/cove-dishwasher-problems) - [Cove Dishwasher: Abnormal Noise or Vibration](/blog/cove-dishwasher-abnormal-noise-2) - [Cove Dishwasher: Does Not Clean or Dry](/blog/cove-dishwasher-cleaning-performance-2) - [Cove Dishwasher: Controls, Display or Error Code](/blog/cove-dishwasher-control-fault-2)
Lead Appliance Repair Technician · 12 years experience
Experienced technician with 12 years specializing in washing machine and dryer repairs across all major brands.
