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We have lived in our house for almost four years. Last winter we had about a week of sub freezing temperatures (not super common for Oklahoma City). Unbeknownst to us the pipe section of a hose spigot burst and we didn't find out until the next Spring (only leaked when the spigot was turned on). There was a small (2 inches) where the pipe was not wrapped in foam right before the spigot and inside that corner.

This is on a corner of our garage, both walls are exterior.

I just had a plumber replace the spigot and he said some fiberglass insulation between the pipe and the exterior wall and a spigot cover should prevent it from happening again. Will that work? I feel like any type of fiberglass insulation wouldn't help because both sides of the wall are not climate controlled. My original plan was to fill the corner with spray foam and make sure the rest of the pipe is properly wrapped with foam. But I'm not sure if that will be sufficient.

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  • It usually depends on how sub freezing the temperatures get. My location would recommend heat tape for pipes, your location might get by with some insulation. Cold air drafts near the pipe is worst.
    – crip659
    Oct 2, 2023 at 20:23

2 Answers 2

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Insulation slows the movement of heat -- it doesn't prevent freezing. Surprisingly, in some cases, a spigot connected to highly-insulated indoor plumbing will still freeze because the insulation restricts indoor heat from warming the pipe.

Your plumber's advice is sound. The spigot cover will reduce the amount of heat that can conduct through the spigot to the outdoors. The fiberglass (or foam) between the pipe and the exterior wall will reduce the amount of heat that can escape toward the outdoors through that wall. Absence of insulation between the garage and the pipe will allow whatever minimal heat is available in the garage to easily reach the pipe.

The question, then, is "how much heat is available in your garage?" Does the garage remain always above freezing? Even though the garage is not climate controlled there's some heat in there. Heat from the engine of an often-used vehicle, heat from the attached house, even heat from the sun shining on a window or door helps.

If the garage does not reliably stay well above freezing then supplemental heat on that pipe will be recommended. Usually that takes the form of electric heat tape/cable.

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Insulation is not a solution, but it helps. Since this is not the home and you didn't state it was critical to have year-round water, you have two options

  1. heat the lines or area so that freezing can't happen.
  2. drain the lines so that there is no water to freeze

Which is right for you is up to you.

  • Heating is more costly to set up and has ongoing costs and prone to failure during electric loss, but very convenient.
  • Draining is almost fail-proof and a not very expensive, one time cost, but is not very convenient.

I would advocate draining the line during the possible freezing months so you don't have to worry about freezes.

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  • You actually don't need to drain it. Shut off the source and open the tap. Any frozen water will "push out" and not burst the pipe. The only way to burst pipe is if the pipe is completely shut. The insulation also won't help much, because it only slows down heat loss, and since the water doesn't generate heat, you're only making the freezing take longer. 8 hours at sub-zero temperature will freeze it unless you actively heat it.
    – Nelson
    Oct 3, 2023 at 8:59
  • @Nelson I've heard that works, but I've always worried that the open end could freeze first can create an ice plug in the pipe that would act as a cap and allow water behind it to freeze and burst the pipe. Oct 3, 2023 at 12:58
  • Even if the ends freeze, what happens is that when the ice is formed further down in the pipes, this creates pressure from the ice to the pipes, which actually melts it. The ONLY way for pipes to burst when freezing is if the valves are completely shut, because otherwise, the water will melt along the pipe and come out the end of the faucet, even if it is frozen first. When you see this in action, you'll have this icicle form from the faucet, and it'll grow out of the faucet as the water inside the pipe freeze and push out from the open faucet.
    – Nelson
    Oct 5, 2023 at 8:46
  • Mechanical pressure creates heat. This is how skates work.
    – Nelson
    Oct 6, 2023 at 1:10

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