If you ever come across a situation where you go to use a machine and the dirty water tank smells so bad that you cannot even turn the machine on, you need to clean and remove the odors from that tank. The most important thing to do when draining the water from the tank is to open it completely, rinse it thoroughly, and always leave the tank lid open. If the lid is open, the tank will dry out properly. If you are in a situation where the machine is extremely smelly, you can use an odor digestor (containing organic chemicals). Fill the tank with lukewarm water, mix in the odor digestor, and let it sit for an hour or two. Finally, drain the tank fully, rinse it again, and leave it open to dry. This process is the same when using a carpet extractor.