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How Does an Anti-Scald Faucet Work?

Hot Faucet

By preventing excessively hot water flow, anti-scald devices protect your family from serious injury and can even save lives. They’re especially important if your household includes young children or an adult who might have difficulty controlling the faucet handles.

As an added benefit, they also keep your water temperature constant so you aren’t always fiddling with the faucet handles. To decide which model best meets your needs, you’ll need to know how these devices work.

Pressure-Balanced (Type P) Valves

The simplest and cheapest anti-scald devices, these valves maintain a balance between the pressure in the hot and cold water input lines. Water pressure is controlled by a piston or diaphragm in the faucet that moves in response to changes in water pressure. If the cold water pressure drops, the piston moves to reduce the amount of hot water leaving the faucet.

During installation, this device must be calibrated to your water temperature. If you raise or lower your water heater temperature any time afterward, the device will have to be re-calibrated.

Thermostatic Mixing (Type T) Valves

Thermostatic mixing valves, or TMVs, respond to changes in temperature rather than pressure. These devices have a chamber in which they mix hot and cold water before it flows out through the faucet. A thermostatic element inside the chamber expands and contracts with changes in the water temperature. As the temperature rises, the element expands to limit the hot water entering the mixing chamber.

TMVs are more expensive than pressure-balanced valves, but they don’t require calibration. They also let you keep your water heater at a higher temperature to kill Legionella and other bacteria.

Combination (type T/P) devices are a third option. These provide a higher level of protection by combining the methods of type P and type T devices. They use a piston to balance water pressure and a thermostatic element to respond to water temperature.

If you’d like anti-scald devices installed or need any other help with your plumbing, contact us at Reliance Home Services in the Greater Los Angeles area.

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