The Necessary Components for Rainwater Collection and Filtration – GreenBuildingAdvisor

By Chuck Bickford | July 28, 2025

Depending on where you live, water may or may not be at the top of your daily concerns. Some folks have an abundance, while others are always looking for the next downpour. Municipal reservoirs and wells serve the majority of areas, but the story may be different if you live out in the hinterland with sporadic rainfall. Rain has always been recognized as a handy source of water, to be collected and stored in cisterns, barrels, or tanks. And as the health of the water supply is threatened by environmental concerns, rain collection is one way for people to obtain water. But the process is more complicated now; rainwater can pick up all sorts of impurities on its way to the storage tank and should be filtered and/or disinfected before it can be safely consumed. For more info, see this article on residential rainwater harvesting and this piece on cisterns and rain barrels.

Member “stephenr” (let’s just call him Stephen) writes in a recent post that he is designing a rainwater catchment system for his house in Maine. He’s planning to install a 700-gallon tank inside the house to protect against frost, and he’s confident about the details of the path from the roof to the tank. What he’s not sure about is the sequence of components from the tank to the tap. He thinks he’ll probably use the rainwater for washing, but he’s thinking about passing the water through a filter system so he can drink it too. Stephen comments, “Here’s what I have: Tank + pump + sediment filter + ultraviolet light (that kills microorganisms) + pressure tank + electric hot water heater + fixtures. Also, I think I need to size the pump to the UV light. Anyone with input on that?”

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