Which device is used on an outside pipe to prevent freezing?

• A. Insulation
• B. Resistor
• C. Tape measure
• D. Pressure relief valve

Answer: (B)

Preventing freezing of an outside pipe is all about keeping heat in and cold air out. Insulation does exactly that by wrapping the pipe and slowing down heat loss to the surrounding chilly environment. With proper insulation, the water inside stays warmer and less likely to freeze, which is the typical method used for outdoor piping.

A resistor is an electrical component that can generate heat when current passes through it, but it isn’t installed on a pipe by itself to prevent freezing. It’s more a part of heating elements used in some heating cables, not the standard preventive device described here. A tape measure serves for measuring, not for temperature protection, and a pressure relief valve is for releasing excess pressure, not preventing freezing. So insulation is the correct choice because it directly reduces heat loss from the pipe to the cold outdoors.