Rain water filtration is necessary any time you are using stored rainwater for drinking, cooking, or bathing — as untreated tank water can harbour harmful bacteria such as E. coli, Giardia, and Legionella, as well as sediment and debris that accumulate over time. It is also essential if your tank hasn't been cleaned in several years, if you've noticed a change in the taste, smell, or colour of your tank water, or if your household includes vulnerable individuals such as young children, elderly family members, or those with compromised immune systems. Even for general household use, filtration protects your appliances and plumbing from sediment damage.