A regular shower head uses 7 to 10 gallons a minute, while a water-saving shower head puts out 2 to 4 gallons a minute. An average shower lasts 12 to 15 minutes, resulting in a use of up to 150 gallons per shower.
In comparison, a full conventional bathtub uses up to 50 gallons, and a whirlpool tub uses up to 80 gallons. Users who leave a conventional faucet on while they brush their teeth use about 10 gallons of water, and men who leave a conventional faucet running while they shave use up to 20 gallons. Using a water-saving faucet for those activities cuts usage to as few as 2 gallons.