Tips to keep your pipes from freezing

Ask the Expert
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Q. When we purchased our circa-1920 center entrance Colonial 10-plus years ago, we created a master suite by merging a closet and a small bedroom and building out up to 8 feet above a 1970s first-floor addition. To get the best layout, we put the toilet against an outside side wall of the new second-floor bump-out. The water supply line to the toilet runs under that new bump-out and comes up through the tiled floor. The only hole in the floor is one just large enough to allow the pipe to come up through it, and there is the usual silver bell-shaped piece that covers the hole.

You know what is coming next. Every winter, during the coldest stretches, that supply line freezes, and I have to thaw the exposed portion with a hair dryer. That took hours during one cold snap last winter. I am concerned that it will burst. My contractor said that it is a fairly big job to remedy and that the original contractor should have wrapped the pipe. To fix it, we need to open up the outside wall and add insulation (or, I suppose, we could hunt for the spot in the ceiling below and try to fix it that way) or open up the bathroom tile. I haven’t yet explored blowing in insulation, but I figure companies would not want to come in for a small job like that. Is there heating tape or a sleeve device I can use to keep it warm in sub-zero weather?

D.B., Newton

A. The right thing to do is to open the area and inspect the installation to determine whether the pipes need to be relocated farther inside the house, whether you can just add insulation, or whether there are air leaks that need to be sealed.

Relocating pipes

A well thought-out building design ensures that pipes are installed on interior walls in conditioned spaces. Remodels in older homes sometimes force you to put pipes in vulnerable areas because of access issues.

Adding insulation

Insulation is a wise investment and can certainly make a difference when it comes to keeping your pipes from freezing. The rim joist is the outermost section of your basement and is often not insulated. Insulating here helps prevent frozen pipes and improves the overall energy efficiency of your home.

That said, there is no guarantee that using pipe insulation will prevent a frozen pipe in vulnerable areas likes exterior walls. Sometimes these freeze-prevention measures are not enough; in which case, it’s time to add heat cables. You cannot bury pre-terminated heat cables (the ones that plug into an outlet) in any inaccessible location such as a wall, ceiling, or floor. A self-regulating freeze-protection heating cable is an energy-efficient option you can consider — a 16-American-wire-gauge cable suited for commercial and industrial applications. It can be installed in any length up to 460 feet and will work in wet or dry locations. A thermostat is required in these applications to ensure that a liquid temperature is properly maintained. The self-regulating freeze-protection cable is installed at the bottom of the pipe, and at the 5- and 7-o’clock positions if two cables are used.

Note: Self-regulating freeze-protection cables are designed to be installed in conjunction with insulation. This includes insulating all valves, tees, and spigots.

Air leaks

A pinhole air leak can cause frigid air to freeze an unprotected water pipe. Seal all holes made from the installation of cable and phone wires, pipes, windows, framing, etc. I suggest using expanding foam. Doing this and insulating your rim joist are two inexpensive steps with a large return on investment.

Don’t forget to keep the heat up in the bathroom or room below.

Rob Robillard is a general contractor, carpenter, editor of, and principal of a carpentry and renovation business. Send your questions to [email protected] or tweet them to @robertrobillard. Subscribe to our free real estate newsletter at