A water tank can look calm on the outside while sediment, biofilm, rust, insects, leaves, and bacteria build up inside. That buildup does not always change the taste or smell right away, which is why a cleaning schedule matters. For most homes and small properties, a potable water storage tank should be cleaned at least once a year. Some tanks need cleaning every six months, especially if they collect rainwater, sit in hot weather, receive untreated well water, or show signs