What is used on an outside pipe to prevent freezing?

• A. Heater
• B. Insulation
• C. Thermostat
• D. Resistor

Answer: (D)

To stop an outside pipe from freezing, you need to keep its temperature above freezing in cold conditions. The direct way to do this is to provide a heat source to the pipe, such as a heater or heat-trace system, which actively adds warmth to prevent the water inside from freezing. A thermostat isn’t the heat source itself but a control that can turn the heater on or off as needed. Insulation helps by reducing heat loss and slowing freezing, but it doesn’t actively raise the pipe temperature. A resistor isn’t a standard method for preventing freezing on pipes. In practice, you’d typically use a heater (often with a thermostat) to reliably keep the pipe from freezing, sometimes in combination with insulation for extra protection.