In a fascinating twist, they found a striking relationship between a shower head’s water pressure and overall water consumption. It turns out that people took shorter showers when the water pressure was greater. For shower heads “dribbling” water at a paltry 16 to 32 psi, showerers used an average of 16 gallons (60.6L) of water. With a more forceful spray of 32 to 49 psi, people used 12.8 gallons (48.3L). When water blasted at 49 to 65 psi, people got done with just 6.3 gallons (24.2L).
https://www.freethink.com/energy/water-pressure