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Edited to add pics.

I live in an old home, built in 1919.

At some point before I bought the home, there was an addition that added a bathroom and three seasons porch. The original foundation is stone, but the addition is block and has a dirt floor in part of it. The addition part of the home is poorly insulated or not insulated at all.

There are pipes that run into the bathroom, from the addition - the sink, toilet and shower. The lines to the sink and supply to the toilet occasionally freeze. The shower never freezes and the toilet can always flush, but sometimes will not refill.

We’ve put fiverglass insulation in the floor joists in that part of the addition and sprayed foam where the pipe enters the home in the block foundation.

There’s a dirt-floor crawlspace in this section of the basement, and I’ve lined that with Astrofoil, in an attempt to hold heat in the space.

We’re considering wrapping the pipes with insulating foam; Will this even help? Is there a better plan?

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    Have you thought through the heat path here? By insulating the floor joists you've reduced the amount of heat that gets to the pipes (I assume--we don't have much info here). Maybe revise to explain the location of the insulation and the pipes in more detail. Ultimately it comes down to keeping the pipes inside the building envelope, not outside it.
    – isherwood
    Oct 30, 2023 at 21:20
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    Or heating the pipes themselves. I've got heat tape wrapped around the pipes at greatest rush, plugged in much of the winter...
    – keshlam
    Oct 30, 2023 at 21:39
  • You want the pipes to be in the warm house air. Pipes in outside walls are bad, pipes under an insulated floor is bad. If pipes must be in the cold, heated pipe tapes can help.
    – crip659
    Oct 30, 2023 at 21:41
  • Insulation keeps in heat. No heat? Then insulation won't make a difference. There's some heat conductance along metal pipes, so your home's internal heat can keep insulated outdoor pipe thawed to an extent, but I'm thinking of an insulated hose bib cover, not even a couple feet of pipe. This area sounds uncomfortable during cold months. Can you add a water shut off for this area during the cold?
    – popham
    Oct 30, 2023 at 21:42
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    @JimStewart yeah, we haven’t had any leaking or bursting. The pipes are Pex tubing. Maybe some foam will be enough!
    – Kael
    Nov 1, 2023 at 12:45

2 Answers 2

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To fix the issue, install heat trace to the water lines (both hot and cold) and then add pipe insulation to keep the added heat in. There are many types, but the simplest option is to measure out the length that you need and buy the appropriate length 'automatic cable kit' from a box store. You can run more than one if needed and you can unplug them when it's the warm season.

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You can install a hot water recirculating pump under the bathroom sink.

These are available as a kit containing everything you need: a near-silent pump, a thermostatic valve and a pair of hoses to connect to your shut-off valves under the sink.

The pump runs continuously, or you can plug it in / switch it on only when the temperature drops below freezing. I don't recommend that you use a timer because outdoor temperature doesn't run on a timer.

The way it works is that the thermostatic valve provides a path for hot water to return to your water heater via the cold water pipes, but only when the valve's temperature falls below 90F. When you first turn it on, the pump will force hot water into the cold water pipe continuously. The crossover valve will gradually warm up, and as soon as the valve reaches 90F, the valve will close and there will be no more flow.

Eventually, the valve will cool off because there is no hot water flow. When the valve detects the temperature drop, it will open slightly and pass a little more hot water into the cold water pipe until the valve is once again at 90F.

This system doesn't waste any water down the drain. It simply circulates water inside your pipes. The system does use some energy keeping your pipes warm, and keeping the pipes in your walls warm is not free.

When in use, your hot water pipe that sometimes freezes will stay lukewarm inside the wall and your cold water pipe in the wall will be tepid but not icy cold. That's all you really need to prevent freezing.

You can turn the device off in the spring to save energy, or you can leave it running if you become accustomed to instant warm water.

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  • Thanks, I’ll check that out. Is there something similar I could install for the toilet?
    – Kael
    Oct 30, 2023 at 22:35
  • @Kael Since both the sink supply and toilet supply were freezing, it's likely that they are getting their cold water from the same pipe. The device under the sink will keep that pipe from freezing for its entire length. So unless the pipe run from that now-tepid pipe is long or it passes through an extra frigid area, the one device should prevent freezing for both fixtures.
    – MTA
    Oct 30, 2023 at 22:57
  • Thanks, I’ll definitely check it out. Unfortunately, we’ll have to wait to see if it works
    – Kael
    Nov 1, 2023 at 12:46
  • @Kael Fair enough, but I can tell you that it works at my house. The previous owner built a second floor and sent water lines and hydronic heating lines through an unheated attic space for a short distance. They all froze up twice my first winter here. Fortunately the lines are PEX so no damage. The hydronic was a whole 'nother project, but bottom line is no more frozen pipes.
    – MTA
    Nov 1, 2023 at 12:53

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