Sometimes, when you’re a teenage boy, you flush a toilet while your sister is in the shower and then wait to hear her scream. At that age, you probably don’t know why flushing the cold water in the toilet makes the water in the shower crazy hot. You just know it annoys your sister. The change in temperature is due to a drop in water pressure from either the hot water or cold water. If the pressure in the cold water goes down, the water temperature goes up and vice versa.
As fun as it might be to harass your sibling, these temperature fluctuations can be a serious safety hazard. Water that’s 160 degrees Fahrenheit or hotter can scald you. In fact, scalding makes up 20% of reported burns. Children and elderly persons have thinner skin and scald more easily. The shock factor that makes your sibling scream can cause some to fall injuring themselves further. Or worse, the shock could induce a heart attack on those who are prone.
An anti-scald valve is a simple device that can help minimize or eliminate this hazard. It works by balancing the pressure between the hot and cold-water supplies. When pressure drops on one side it limits on the other. Some authorities have jurisdiction are now requiring these safety devices.