You use the wrong showerhead.
How old is your showerhead? If it was manufactured before the early ’90s, it could have a flow rate of 5.5 gallons per minute. Compare that to current showerheads on the market, which are required by federal regulations to have a flow rate of just 2.5 gallons per minute—or even less. If your home contains older fixtures, check to see if your showerhead needs an update. There are countless options available, but you can expect to invest a minimum of $10 for a decent one.