People used to think showers were less wasteful than tub baths. They failed to take into consideration the fact that many of us spend 10 to 20 minutes or more in the shower. Since most showers pour out between 5-10 gallons per minute, that can add up in a hurry.
A partially filled tub uses far less water than a long shower, while a short shower uses less than a full tub. Time yourself next time you step under the spray. The odds are you really don't need to stand there that long, nor do you need the shower running at a full, hot blast.
Limit showers to five minutes. Buy a portable, wind-up kitchen timer. Have your teenagers set the timer before getting into the shower, limiting their time. Use the minimum amount of water needed for a bath by closing the drain first and filling the tub only 1/3 full. Put a stopper in the tub before turning on the water. Adding hot water later can warm the initial burst of cold water.
Keep showers short with pressure at low force. Fix drips promptly. Use a low-flow shower head, flow restrictor, or cut-off-valve, which lets you shut off water at the shower head while soaping up and shampooing, without changing the faucet setting.