A shower or bath faucet that unpredictably spits out scalding-hot water can be a serious hazard. It takes just three seconds for a child to sustain a third-degree burn from water that’s heated to 140 degrees Fahrenheit—a typical tap-water temperature in many bathrooms.

The simplest scald-prevention measure you can take is to set the thermostat on your water heater at 120 degrees. However, the only way to prevent temperature fluctuations is to install tub and shower valves with built-in scald protection.

Temperature fluctuations are caused by changes in water pressure: When someone flushes the toilet, for example, water pressure drops in the cold-water pipes, altering the mix of hot and cold at the shower or tub. A rapid change in the balance of hot and cold water causes a scalding spray of hot or—if hot-water pressure drops—a chilling blast of cold. To combat this problem, you can install either a pressure-balancing or a thermostatic valve.

A pressure-balancing system will automatically adjust the mix of hot and cold water to compensate for changes in water pressure. A thermostatic valve will self-adjust in response to changes in temperature. Some manufacturers offer a control valve that does both. Installation for all of these valves is the same as for a conventional valve.

Most states require the use of pressure-balancing fixtures in new construction. While it’s unlikely that you’ll be required to use scald-free valves in a bathroom remodel, it makes good sense to take a precaution that’s so simple and has so much potential to prevent injuries. Prices are within reach even if you’re aiming for a more budget-friendly remodel: Pressure-balancing valves start at less than $100.