The SharkBite Heat guard 110-D is a Temperature Actuated Mixing Valve that mixes hot water with cold to deliver tempered water at a controlled temperature to 120��F maximum. The Heat guard 110-D is designed to assist in the prevention of scalding. The SharkBite Heat guard 110-D valve delivers water at a maximum of 120��F, allowing the heater to be set at 140��F or higher, thus providing a greater effective volume of hot water.