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Quick answer: To clean a Roborock dirty water tank: pull the tank out of the dock, tip out the used water, rinse it under warm running water, and use a bottle brush or old toothbrush to scrub the corners and the float sensor where sludge collects. Once a week, fill the clean water tank with a white-vinegar solution and run the dock’s self-clean cycle to flush the lines, then dry the tank with the lid off. Do the rinse after every mopping run and the vinegar flush weekly.
Rinsing the tank when you remember isn’t enough — the smell and the sludge come from the spots a quick rinse misses. Here’s the full routine, and how often each part actually needs doing.
What you need
- Warm water and your kitchen tap
- A bottle brush or an old toothbrush (for corners and the sensor)
- White vinegar — for the weekly flush
- Optional: a little dish soap, and an antibacterial spray for a deeper reset
Step by step
1. Remove the dirty water tank. On most Roborock docks the dirty water tank is the front or top reservoir — check your model, as the layout differs between the S-series, Qrevo and older units. Lift it straight out.
2. Tip out the used water. Empty it down the sink. Don’t let it sit — used mop water is the source of the smell, and the longer it stands the worse the tank gets.
3. Rinse under warm running water. Warm (not hot) water loosens the greasy film that mop water leaves behind. Swirl it around and tip it out two or three times.
4. Scrub the corners and the float sensor. This is the step people skip and it’s the one that matters. A bottle brush or toothbrush gets into the corners and around the little float/level sensor, where a grey-brown sludge collects. That sludge is bacteria — if you leave it, the tank smells again within a day. A drop of dish soap here helps break up the grease; rinse it out fully afterwards.
5. Wipe the lid and seal. The rubber seal and the underside of the lid trap grime and grow mould. Wipe them with a cloth (and antibacterial spray if it’s been a while).
6. Dry it with the lid off. Shake out the water and leave the tank to air-dry with the lid open before putting it back. A dry tank can’t grow the bacteria that causes the smell — this single habit prevents most repeat problems.
The weekly vinegar flush
Rinsing cleans the tank, but the dirty water gets there through the dock’s mop-wash system and internal lines — and those build up biofilm you can’t reach by hand. Once a week:
- Add a teaspoon of white vinegar to the clean water tank (or a 1:1 water-vinegar mix for a heavier build-up).
- Trigger a self-clean / mop-wash cycle from the Roborock app. The vinegar runs through the wash tray and lines and ends up in the dirty water tank.
- Empty and rinse the dirty water tank as soon as the cycle finishes — don’t leave the vinegar water sitting in it.
Vinegar is safe for the plastics and seals and is the method Roborock’s own maintenance guidance points to. If you want the full breakdown of what’s safe, see can you put vinegar in a robot vacuum.
How often to clean each part
| Task | How often |
|---|---|
| Empty + rinse the dirty water tank | After every mopping run |
| Scrub corners + float sensor | Weekly |
| Vinegar self-clean flush | Weekly |
| Wipe lid, seal and dock wash tray | Weekly |
| Deep clean with antibacterial spray | Monthly, or whenever a smell returns |
Keep it to that schedule and the tank stays clean and smell-free. Fall behind on the after-every-run rinse and the sludge builds faster than the weekly clean can keep up with.
Frequently Asked Questions
How often should I clean my Roborock dirty water tank?
Empty and rinse it after every mopping run, and do a deeper clean once a week — scrub the corners and float sensor, wipe the lid and seal, and run a vinegar self-clean cycle. The after-every-run rinse is the one that prevents sludge and smell from building up.
Can I put the Roborock dirty water tank in the dishwasher?
No — the tank has electronic contacts and a float sensor that a dishwasher's heat and jets can damage. Clean it by hand with warm water and a bottle brush, and use vinegar or a little dish soap for build-up.
What is the grey sludge in my Roborock dirty water tank?
It's bacterial biofilm — a mix of dirt, grease and bacteria from used mop water that collects in the corners and around the float sensor. Scrub it out weekly with a brush; if you leave it, the tank smells again within a day even after rinsing.
Should I use vinegar or bleach to clean the tank?
Use white vinegar. It kills the bacteria causing the smell, is safe for the tank's plastics and seals, and can be run through the dock's self-clean cycle. Avoid bleach in the water lines — it's harsher on the seals and can react with residue. Vinegar is the standard, safe choice.
