Why is shower head GPM or flow rate important?

GPM means Gallons Per Minute.

Federal, state, and local governments regulate shower head GPM flow rates, because the potential for water and energy savings are significant.

A standard 2.5 GPM shower head uses 2.5 gallons of water each minute. That's 25 gallons for a 10-minute shower.

VS.

A low-flow 1.8 GPM shower head uses 1.8 gallons of water each minute. That's only 18 gallons for a 10-minute shower.

According to the EPA showering is one of the leading ways we use water in the home, accounting for nearly 17 percent of residential indoor water use - for the average family, that adds up to nearly 40 gallons per day. That's nearly 1.2 trillion gallons of water used in the United States annually just for showering.