How do you clean a carpet cleaner machine after use?

Empty and rinse both the dirty-water and clean-water tanks, remove and rinse the brush roll cover and any hair wrapped around the rollers, and rest the machine on its back to check the hose mouth and spray nozzles for clogs, per Bissell's own maintenance instructions. Wrap the cord and store the machine with both tanks open and fully dry, not sealed shut while damp.

Why does my carpet cleaner smell musty?

Mold needs oxygen, moisture, and a food source to grow, and a sealed tank with leftover soapy water sitting inside checks all three boxes. The smell almost always traces back to storing the machine with a tank that wasn't fully emptied and dried, not a defect in the machine itself.

How often should you deep clean a carpet cleaner?

Bissell recommends a deep clean every 3-6 months, flushing the internal hoses and spray nozzles with a mix of white vinegar and warm water to clear out residue and mold that a quick tank rinse doesn't reach. Run the solution through an empty cycle over a sink or tub rather than onto carpet.

Can you run vinegar through a carpet cleaner?

Yes — a diluted white vinegar and warm water mix is the standard DIY deep-clean flush recommended for clearing residue and mold from internal hoses and nozzles every few months. Run it through the machine's own spray-and-suction cycle over a sink or bathtub, not directly onto carpet, then follow with a plain water flush to rinse out the vinegar smell.

Is it bad to leave water in a carpet cleaner tank?

Yes. Leftover water — even a small amount — sitting in a sealed tank between uses is the single biggest cause of the musty, mildew smell that eventually transfers back onto your carpet during the next clean. Empty and rinse both tanks after every use, and let them air-dry open before storing the machine.

How to Clean a Carpet Cleaner Machine (2026): Stop the Musty Smell Before It Starts

Quick Answer: Empty and rinse the dirty-water and clean-water tanks after every single use, clear hair and debris from the brush roll, and check the hose mouth and nozzles for clogs — then let both tanks dry fully open before storing, per Bissell’s own maintenance instructions. Every 3-6 months, run a diluted white-vinegar-and-warm-water flush through the machine’s hoses and nozzles to clear residue a quick rinse misses. Skip this and the machine’s tank becomes the exact combination mold needs to grow — oxygen, moisture, and a food source — which is why a “broken” carpet cleaner that smells musty usually just needs a real cleaning, not a repair.

It’s an easy blind spot: a machine built to extract dirty water from your carpet spends every cycle full of dirty water itself, and that water doesn’t just disappear when you’re done. Skip the after-use routine a few times and the smell that was supposed to leave your carpet starts coming back out of the machine instead. Here’s the actual maintenance schedule, sourced from manufacturer instructions rather than guesswork.

After every use, in order

Step	What to do	Why it matters
1. Empty both tanks	Dirty-water tank into a utility sink, clean-water tank too even if solution is left over	Leftover solution or dirty water is the #1 source of mildew smell in storage
2. Rinse both tanks	Hot water rinse, swirl and dump	Removes soap residue that would otherwise cake on and feed mold
3. Clear the brush roll	Remove the cover, pull hair/debris off the rollers, rinse under running water	Trapped hair holds moisture against the roller and housing
4. Check the hose and nozzles	Rest the machine on its back, look for clogs at the hose mouth and spray tips	A clogged nozzle is the most common cause of weak or no spray next time
5. Air-dry before storing	Leave both tanks open (not sealed shut) until fully dry, then wrap the cord	Mold needs moisture to grow — a sealed, damp tank is exactly that environment

By the numbers

3-6 months — how often Bissell recommends a full internal deep clean, flushing hoses and spray nozzles rather than just rinsing the tanks, per Bissell’s official maintenance guidance.
3 — the number of things mold needs to grow inside a sealed tank: oxygen, moisture, and a food source (leftover solution residue supplies the last one).
2 — the number of tanks most machines have (clean and dirty), and both need emptying and rinsing after every use, not just the visibly dirty one.
0 — how much standing water should be left in either tank before you put the machine away. Even “a little” left in a sealed tank is enough to start a musty smell.

1. Empty and rinse both tanks — every time

Empty the dirty-water tank into a utility sink and give it a real rinse, not just a dump. Then do the same with the clean-water tank, even if there’s unused solution left in it — soap residue left to sit is exactly the kind of buildup that feeds mold between uses. This is the single step that prevents most musty-smell complaints, and it takes under a minute.

Deep-clean solution / descaler

~$8-15 · for the 3-6 month internal flush, not everyday rinsing

A dedicated machine-cleaning solution (or plain white vinegar diluted with warm water) clears residue a tank rinse alone can't reach, inside the hoses and spray nozzles.
Run it through the machine's own cycle over a sink or tub, then flush with plain water afterward so vinegar smell doesn't transfer to your next carpet clean.
Need the machine's own solution for actual carpet cleaning, not maintenance? See our best carpet cleaner solution picks.

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2. Clear the brush roll after every use

Pet hair and carpet fibers wrap around the brush roll fast, and a roller packed with debris holds moisture against the housing long after the rest of the machine has dried. Pop the brush roll cover, pull off anything wrapped around the rollers by hand, then rinse the rollers themselves under running water before letting them air-dry. Machines that see regular pet-hair duty — see our best carpet cleaner for pets picks — need this step checked more often than a pet-free household would.

3. Check the hose and nozzles for clogs

Rest the machine on its back and look at the mouth of the hose and the spray nozzles for stubborn hair or debris. A clogged nozzle is the most common reason a machine sprays weakly or stops spraying entirely on the next use — if you’re already dealing with that symptom, our carpet cleaner not spraying troubleshooting guide and Hoover troubleshooting guide walk through the fix in more depth than a routine post-use check needs.

4. Let it dry fully open before storing

This is the step most people skip. Wrapping the cord and putting the machine straight into a closet with both tanks still damp — even after rinsing — seals in exactly the moisture mold needs. Leave both tanks open until they’re genuinely dry, then store the machine in a protected, dry area. A machine that lives somewhere humid, like a garage, needs longer air-dry time before the tanks go back on.

The 3-6 month deep clean

A quick after-use rinse doesn’t reach everything. Residue and mold can build up inside the internal hoses and spray lines even when the tanks themselves look clean, which is why Bissell’s own guidance calls for a deeper flush every 3-6 months: run a diluted white vinegar and warm water mix through the machine’s normal spray-and-suction cycle, aimed into a sink or bathtub rather than onto carpet, then run a second cycle with plain water to clear out any lingering vinegar smell. It’s the same wet-pass/dry-pass mechanic covered in our how to use a carpet cleaner guide — you’re just running it empty, into a drain instead of a carpet.

Common mistakes that cause the musty smell

Storing a tank with any water left in it. Even a small amount sealed inside a closed tank is enough to start mold growth before the next use. Skipping the brush roll. Hair wrapped around the roller stays damp long after the rest of the machine feels dry. Never doing the deep flush. A tank rinse alone doesn’t reach inside the hoses and nozzles, where residue quietly accumulates over months. Storing in a humid space, like a garage, without extra dry time. The tanks need to be genuinely dry, not just rinsed, before they’re sealed back on the machine.

The bottom line

The machine that pulls dirty water out of your carpet needs the same basic care in return: empty and rinse both tanks after every use, clear the brush roll, check for clogs, and let everything dry fully open before storing it. Add a vinegar-and-water flush every 3-6 months and a musty-smelling machine — one of the most common carpet cleaner complaints — mostly stops happening. If your machine already smells musty despite regular rinsing, the fix is usually that deep flush, not a new machine. And if the smell is coming from the carpet itself rather than the machine, that’s a different problem — see our how to disinfect carpet guide for what actually kills the bacteria behind it.