The short answer
Water on the floor under a Bosch SMU-series dishwasher is placed before it is fixed, and on this family the placing is easier than usual because an undercounter fit narrows the list straight away. Water at the front of the door is the seal, the door's own alignment or the dispenser; a machine that empties itself and then refuses to fill has found water in its own base pan and is telling you the leak is underneath.
What you observe
- A wet patch directly in front of the door — Water that ran down the inner face of the door and over the lip. That is the seal or the door sitting proud.
- Water appearing at one side of the plinth — Something under the tub is dripping onto the base and finding the lowest exit.
- The machine drains without being asked and will not fill — Leak protection has found water in the base pan. It is protecting the floor and it is right.
- A swollen cabinet edge or lifted flooring beside the machine — A slow leak that has been running longer than the puddle suggests.
- NEAR MISS - water only appears when the sink is used — That is the waste connection above the machine rather than the machine itself, and it is fixed under the sink.
Likeliest causes here
- Foam from the wrong detergent — Hand detergent or too much of a gel makes suds that climb past a perfectly good seal. First on this family, and for a reason that belongs to the platform: it is the cause that leaves no trace once the floor is dried.
- The door gasket hardened, displaced or dirty — The seal only works while it is soft and seated all the way round, and a strip of grease along the bottom of it is enough to break the line. Second here, and close enough behind the first to be checked in the same pass: it is the part of this machine that is handled most often and inspected least.
- The drain or supply connection under the sink — The clamp at a disposer spigot and the fitting at the shut-off are the two joints most often disturbed and least often re-checked. Ranked third on these models: usually the first thing that has been worked on recently.
- The inlet fitting or the fill valve — A weeping fitting drips only while the machine is filling, which is why it is so often missed. Last, and the ranking is the point: a dry paper towel taped under the fitting settles it overnight.
- Where this ranking departs from the brand-generic page — The cause that moves is foam from the wrong detergent. It leads on this family because the machine slides under a worktop that is not its own, with the plumbing crowded in behind it. That is a property of the platform rather than of the brand, which is why the page above this one cannot rank it the same way.
Check in this order
- Read the label on whatever is in the dispenser — Anything not made for a dishwasher, or too much of the right thing, produces exactly this leak.
- Run a finger all the way round the door seal — Feel for grease, hard spots and a strip that has crept out of its channel.
- Dry everything under the sink and run a cycle — Watch the clamp at the disposer and the fitting at the shut-off through a fill and a drain.
Before you open anything
Safety
Shut the water off at the valve under the sink and unplug the appliance or switch off its breaker before removing any panel - a capacitor can hold a charge after the power is off, and on a leaking machine the mains connection is sitting in the wettest part of the cabinet. Dry the floor before you test anything, so the next drop you see is new.
When to call
The door seal, the dispenser, the rinse aid well, the detergent and everything under the sink are owner ground on these models. The line is the base pan: once the machine is emptying itself and refusing to fill, the water is beneath the tub and finding it means the machine on its back with the base plate off.
Nearest pages
Lead Appliance Repair Technician · 12 years experience
Experienced technician with 12 years specializing in washing machine and dryer repairs across all major brands.
