The EPA estimates that the average American uses 82 gallons of water per day. For a family of four, that’s 328 gallons a day or nearly 120,000 gallons a year. Families can save a lot of water by taking simple measures: For example, the EPA estimates families save 13,000 gallons of water per year by replacing inefficient toilets — and 9,400 gallons of water annually by repairing leaks.