A. Pressure balance valves help prevent scalding by compensating for changes in pressure on the hot or cold supply lines. When water use elsewhere in the system causes the pressure of either the hot line or the cold line to fluctuate, like when a toilet flushes, the internal piston in the Symmons Temptrol pressure balance shower valve adjusts automatically to instantly and continually equalize or "balance" the hot and cold water pressure. This keeps the water temperature consistent, so you don't have to worry about shocks of ice cold or burning hot water.