Like nonpotable systems, storage tanks can be made of stone, cement, metal, wood, or fiberglass. But if you're planning on showering with or drinking rainwater, stone and cement can leach minerals, and galvanized tanks can release zinc in the water unless a PVC liner is used (zinc from galvanized roofs is filtered out before being stored).
Fiberglass tanks, though hardly the most attractive, are easily the cleanest and most durable. You'll need to keep the tank out of the sun in order to avoid algae growth. Tanks are sometimes buried, either partially or fully, to keep the water cool or to hide the tanks (and to prevent the water inside from freezing). However, buried tanks add costs for excavating and can't easily be cleaned. A better option is to shade the tanks to ensure that only rain—and not sunlight—gets in.
Shown: Inside the shed, a
1horsepower electric jet pump and a pressure tank push the water through two carbon filters and past a UV disinfecting light before it goes back to the house via a
1½-inch PVC pipe.