Can I use rainwater as drinking water for my home?

You can, but it must be treated, and the TWDB cautions that rainwater is not a reliable drought-proof sole source. The Texas Manual on Rainwater Harvesting says drinking-water systems need treatment beyond basic leaf screens, such as fine cartridge filters (for example 5-micron then 3-micron) followed by ultraviolet light or other disinfection, plus regular testing for germs like E. coli. It recommends diverting the first flush, at least 10 gallons per 1,000 square feet of roof, and keeping tanks covered with screened vents against mosquitoes. Metal roofs suit drinking-water systems; asphalt shingle roofs are recommended for irrigation only. If the home also has city water, backflow protection and utility notice are required.

Check your local rule. This varies by state, county or city. Your permitting office has the final word; the official lookup pages below show you who that is.

Sources

• The Texas Manual on Rainwater Harvesting, 3rd EditionTexas Water Development Board (TWDB)
• Rainwater Harvesting FAQTexas Water Development Board (TWDB)