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Q.What’s the best way to insulate plumbing supply lines in an exterior 2x6 wall?

A.Master plumber Rex Cauldwell responds: This is like a trick question. The answer is, you don’t. My rule is that if it is cold enough to have the pipes insulated from freezing, then you shouldn’t put the pipes in the outside wall. By insulating them, all you do is keep the heat from inside the house from getting to the pipes. Insulation just slows down the freezing process, it doesn’t prevent it.

Stay out of the exterior wall and go through the floor. For those of you who ignore my advice, you have to use heat tape and closed-cell foam pipe insulation.