The most popular rain barrels typically hold about 50 gallons of water, ... For larger gardens or home use, a barrel that’s between 80 and 100 gallons is usually sufficient.

Barrel capacities range from under 50 to more than 300 gallons. If you find that you'll be using a large amount of water, you can connect two or more rain barrels in a series or install barrels ...

All you have to start with is one barrel for your water collection system and you could get money back. From his roof, Redwood City resident Eric McCrystal can collect 450 gallons of rainwater.

A 450-gallon tank and a 55-gallon tank from the city that is used daily to water their plants. "That brief rain that lasted maybe about a day, we filled that barrel up in less than 30 minutes ...