How many gallons for a 15 minute bath?

Water use in a show er depends on the duration of the shower. A n answe can only be provided in gpm.

Present American national energy policy act (EPAct) standards mandate that all showerheads manufactured in the U.S. have a maximum flow rate of 2.5 gpm (9.5 Lpm). While some exceed this others use 1.5 gpm or less (5.7 Lpm).

In the past many showerheads exceeded 5 GPM (18.9 LPM).