ThermaHeat Heating Pads are designed and engineered to protect RV holding tanks and pipe from freezing. All tank heaters have a built in thermostat that will turn on at 45 F (5C) and off at 67 F (20 C). Pipe and elbow heaters are not thermostatically controlled and must be hard wired to a separate on/off switch. All heaters have an easy to install peel-e-stick adhesive that adheres to any clean surface. One tank heater will protect up to a 40 gallon holding tank. 12V DC. All heaters carry a 2-year .