With the onset of summer heat and sunshine, many people turn to their lawn sprinklers to water parched lawns. But traditional watering can be expensive and wasteful. Using free water stored in a rain barrel is an increasingly attractive option. For every inch of rain that falls on a 500 square foot roof equals 300 gallons of water, a potential savings of up to $35 dollars a month on your water bill. You can find rainbarrels in a variety of styles at your home or hardware store.