The answer to 'why is my vacuum stained' is that there are a few common causes, including dirt and debris buildup, spills or leaks, and improper cleaning. Stains on the vacuum can be caused by things like pet hair, dust, and food particles getting trapped in the hose, canister, or other parts of the vacuum.
The symptoms of a stained vacuum may include visible discoloration, a musty odor, or reduced suction power. To fix this, you'll want to thoroughly clean the vacuum, including removing the hose, filter, and other components to scrub away any built-up grime. If the stains persist or the vacuum isn't working properly even after cleaning, it may be time to call in a professional vacuum repair technician.