The short answer
Water on the floor at a Cosmo dishwasher usually comes from the door seal, the fill connection or the drain connection under the sink, not from the tub itself. Find where the water first appears and when in the cycle, and the source narrows immediately. Detergent foam is a surprisingly common cause and costs nothing to rule out.
What you are actually seeing
- Water on the floor directly in front of the door — Means: on-page
- A wet cabinet floor under the sink rather than in front of the machine — Means: on-page
- Water appearing only during the fill, or only during the drain — Means: on-page
- Foam escaping around the door — Means: on-page
- Water appearing after the machine was moved or the kitchen was worked on — Means: on-page
- Water standing inside the tub with a dry floor — Means: different-fault — Go to: cosmo-dishwasher-drainage-failure
- Condensation on the worktop above the door at the end of a cycle — Means: different-fault — Go to: cosmo-dishwasher-door-seal
- Body: Match what you see before you take anything apart. Water on the floor directly in front of the door. A wet cabinet floor under the sink rather than in front of the machine. Water appearing only during the fill, or only during the drain. Foam escaping around the door. Water appearing after the machine was moved or the kitchen was worked on. Some near-miss symptoms belong on a different page: Water standing inside the tub with a dry floor points at a drain fault, covered on cosmo-dishwasher-drainage-failure; Condensation on the worktop above the door at the end of a cycle points at normal venting rather than a leak, covered on cosmo-dishwasher-door-seal.
Causes, ranked for this machine
- The door gasket is dirty, displaced or holding a lodged object — Why this rank: First because it is free to check, it is the seal that faces you, and food debris in the gasket channel is extremely common
- Too much detergent or the wrong detergent producing foam that escapes the door — Why this rank: Foam climbs where water cannot and gets past a seal that holds water perfectly well
- A loose or leaking fill connection or drain connection under the sink — Why this rank: This produces a wet cabinet with a dry kitchen floor, which is the single most useful observation an owner can make
- The machine is not level, so water sits against one part of the door — Why this rank: Levelling decides where water in the tub rests, and it is disturbed whenever the machine is moved
- A failed door seal, a cracked sump or a leaking pump seal — Why this rank: Last because it needs a part and everything above it is free
- Body: Ranked for a built-in kitchen dishwasher with an electronic control, a manual filter and a drain hose running to a disposer or an air gap. Most likely: The door gasket is dirty, displaced or holding a lodged object. First because it is free to check, it is the seal that faces you, and food debris in the gasket channel is extremely common. Next most likely: Too much detergent or the wrong detergent producing foam that escapes the door. Foam climbs where water cannot and gets past a seal that holds water perfectly well. Third: A loose or leaking fill connection or drain connection under the sink. This produces a wet cabinet with a dry kitchen floor, which is the single most useful observation an owner can make. Fourth: The machine is not level, so water sits against one part of the door. Levelling decides where water in the tub rests, and it is disturbed whenever the machine is moved. Fifth: A failed door seal, a cracked sump or a leaking pump seal. Last because it needs a part and everything above it is free.
What to check, in order
- Establish whether the floor is wet in front of the machine or the cabinet is wet under the sink
- Wipe the door gasket clean and run a finger round it for debris or a displaced section
- Run one cycle with a small measured dose of dishwasher detergent and nothing else
- Check the machine is level and does not rock
- Body: Each check rules out the causes above it. First, establish whether the floor is wet in front of the machine or the cabinet is wet under the sink. Second, wipe the door gasket clean and run a finger round it for debris or a displaced section. Third, run one cycle with a small measured dose of dishwasher detergent and nothing else. Fourth, check the machine is level and does not rock.
Checks you can safely make yourself
- Dry the floor and the cabinet under the sink completely, run a short cycle and note which one becomes wet first — Tools: towel — Time estimate: one short cycle
- Wipe the whole door gasket with a damp cloth and run a finger round it, removing debris and reseating any displaced section — Tools: cloth — Time estimate: a quarter of an hour
- Run a cycle with a single measured dose of dishwasher detergent and no additive, and watch the door for foam — Tools: measuring spoon — Time estimate: one cycle
- Open the cabinet under the sink, dry every fitting on the fill and drain lines, then run a cycle and feel each one for the first damp spot — Tools: paper towel, torch — Time estimate: one cycle
- Check the machine sits level and does not rock, adjusting the feet through the lower panel if it does — Tools: spirit level, spanner — Time estimate: half an hour
- Body: Checks an owner can make with the machine switched off at the breaker, or by watching a cycle. Step one: Dry the floor and the cabinet under the sink completely, run a short cycle and note which one becomes wet first. Tools: towel. Time: one short cycle. Step two: Wipe the whole door gasket with a damp cloth and run a finger round it, removing debris and reseating any displaced section. Tools: cloth. Time: a quarter of an hour. Step three: Run a cycle with a single measured dose of dishwasher detergent and no additive, and watch the door for foam. Tools: measuring spoon. Time: one cycle. Step four: Open the cabinet under the sink, dry every fitting on the fill and drain lines, then run a cycle and feel each one for the first damp spot. Tools: paper towel, torch. Time: one cycle. Step five: Check the machine sits level and does not rock, adjusting the feet through the lower panel if it does. Tools: spirit level, spanner. Time: half an hour.
Safety first
Safety
Switch off at the breaker before reaching behind or under the machine, and dry the floor before you work. Water plus a live appliance under a kitchen cabinet is the most common way owners get hurt on this job. 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
Call a technician when the gasket is clean and intact, the detergent is correct and dosed low, every connection under the sink is dry, and the machine is level, and water still appears. A cracked sump or a failing pump seal needs the machine pulled out and the lower panel removed.
Nearest pages of the same kind
Generalized information
This page is generalized across the Cosmo dishwasher line. Front-control and top-control machines, and panel-ready and stainless fronts, share the ranking above but not every part, and this page does not cover a specific model or control revision. Family- and model-specific pages, where they exist, are linked below.
Links: - [Common COSMO Dishwasher Problems](/blog/cosmo-dishwasher-problems) - [COSMO Dishwasher: Abnormal Noise or Vibration](/blog/cosmo-dishwasher-abnormal-noise) - [COSMO Dishwasher: Does Not Clean or Dry](/blog/cosmo-dishwasher-cleaning-performance) - [COSMO Dishwasher: Controls, Display or Error Code](/blog/cosmo-dishwasher-control-fault)
Lead Appliance Repair Technician · 12 years experience
Experienced technician with 12 years specializing in washing machine and dryer repairs across all major brands.
