At their best, temperature and pressure-balance valves will protect you from discomfort. In more serious situations, they can protect you or your children from scalding burns. They are two different options to consider if you want better control of your shower’s temperature, especially to safeguard against unexpected temperature shocks from changes in water pressure. These changes can be caused by toilets flushing, the dishwasher running or other situations. If you are considering installing either of these options, talk to Tim Hmelar and his team at The Kitchen and Bathroom Company of Palo Alto, for great advice.
In essence, both pressure-balance valves and thermostatic valves provide scald protection. They are installed in either the shower or bathtub wall, where the controls are. Pressure-balance valves have a diaphragm inside them that moves with the change in water pressure. When it changes, they immediately rebalance the pressures of hot and cold water, keeping the temperature at about two or three degrees above or below its previous level. If the cold water supply stops, they will reduce the water flow, to prevent burns from the hot water. These valves van have a problem with flows, because when the pressure of cold water dips, it reduces the pressure of hot water as well, to keep the temperature the same.
A thermostatic shower valve is a little bit more complex and more expensive, but they offer better performance. Most have 3/4 inch inlets that allow for maximum flow and volume control. They normally have two controllers, one which sets the volume and the other that controls the temperature. The scald setting on a thermostatic valve limits the actual temperature, regardless of if you turn up the temperature on the water heater.