WetVac W31 supports self-cleaning, which will automatically clean and dry the rolling brush. However, the following issues may cause the WetVac to have a musty smell:

1. The dirty water tank has not been cleaned thoroughly;
2. There are dirt and debris stuck on the rolling brush;
3. The sponge filter has not been cleaned for an extended period of time.

It is recommended to follow the voice prompts to clean the dirty water tank after each use. Also, please rinse and dry the sponge filter and rolling brush regularly.

If you need any further assistance, please contact us.