We have 3/4 inch copper pipe that run on the outside of the house from the water heater to the inside about 20 feet. What should I wrap the pipes with to keep them from freezing and exploding? I live in Phoenix,AZ and I've talked to 2 people that have had their pipes burst. Please help.

 

If it is exposed to the weather, you may want to consider installing a thermostatically controlled heat tape to the exposed pipe and wrapping in a 4" wide kraft fiberglas insulation made for that application. You could even consider the possibility of building a boxed in raceway to cover it and trap warmer air from the building. Insulation alone won't get the job done in an area subject to cold. You may want to consider relocating the pipe.

 

Hi, here in new hampshire (zero degrees today!) I live in a mobile home park. My water main is 3/4" copper 12' long that feeds the MH. We all use the heat tape with the thermostat taped FLAT to the pipe as per the manufacturers intructions. Comes from all the big box stores. We then cover it with the 4" insulation and then we cover that with the 6" black plastic irrigation ribbed piping as a raceway. the black pipe is pre slit down one side and easy to install over the insulation. The slit when kept on the bottom keeps your insulation dry. If it works here in N.H. it will surely work in AZ. Hope this helps.
P.S. - make sure you have a weather proof electrical outlet to plug the heat tape directly into. Here we are not allowed to use extention cords for this purpose.

 

Im with both go for the heater tape. most will self control.

 

It is odd that you would mention "self control" on the units. Some have a button that must be in the proper position against the pipe to detect the temperature of the pipe, not the atmosphere, which is fine. You can back that up with a thermo block which detects atmospheric temperature. I use one of them in my wife's chicken palace to keep them warm. It causes the heat lamp to come on at about 36 and go off at about 38.