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Community and Q&A

Insulate cold water pipes

Pauld2024 | Posted in General Questions on

Replaced galvanized pipes wth copper about 15 years ago.
Current hot weather in California causes extreme heat in attic despite solar attic fan and gable vents.
Cold water in pipe line is extremely warm and warm water is now in toilets
Fear warm water may crack toilet tanks and ruin flooring.
How best to insulate these cold water pipes from water getting warm?
Company which did insulation spoke of 3″ wall around these pipes.
Can you explain what this is and best way to insulate these pipes?

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  1. GBA Editor
    Martin Holladay | | #1

    I have never heard of pipe insulation being called "3 inch wall."

    Here is what pipe insulation looks like. You can buy it in most hardware stores or lumberyards. The most common types are made of foam, and they come split lengthwise so they are easy to install.


  2. Pauld2024 | | #2

    Martin I have this insulation on most of the piping but it is not enough to keep heated water from occurring in the lines. There is a You Tube video that shows you surround the pipe after you place the pipe insulation as you show with the insulation laid on the attic floor. You cut a wedge of this Pink Panther type roll and then place it around the insulated pipe. The video is for pipes in the walls but I suspect the same process would be done for the horizontal pipes.
    I can only believe this is what was meant by a 3" wall.
    Your thoughts are welcomed.
    Please view You Tube video


  3. Expert Member
    Dana Dorsett | | #3

    The problem is that the pipes are in a ~130-140F attic, above the attic insulation(?). If there's room to blow 8-10" of cellulose over the top of those pipes it'll probably take care of the worst of it. Simply wrapping the pipes in 3" of fluff probably isn't going to do much- the idea is to have at least as much insulation above the pipe as there currently is below, so that it is at a cooler temperature layer within the total insulation boundary.

    Ideally the plumbing would all be run fully inside the thermal boundary of the house, but that's often difficult to do as a retrofit in a slab-on-grade house.

  4. rocket190 | | #4

    If you are concerned about 'hot' water ruining your toilet, your concerns are misguided. In the old days (and maybe even now) toilets were often plumbed with a hot water supply line to prevent the tank and bowl from sweating. Now that most homes are conditioned, this is less of a problem.

  5. user-4524083 | | #5

    Paul - I agree with Rick. You need to measure the temperature of the water after a flush with an inexpensive thermometer from the hardware store. You'd be talking about a 50-60 degree rise at the most, not enough to crack a porcelain fixture, I wouldn't think.

  6. charlie_sullivan | | #6

    I agree that hot water is not likely to damage a toilet, but it's still annoying when you want a glass of water in the bathroom and it comes out hot.

    As Dana says, "the idea is to have at least as much insulation above the pipe as there currently is below, so that it is at a cooler temperature layer within the total insulation boundary."

    If the pipes were on the attic floor, you could do that by laying a fiberglass batt over the top of them.

    If they are far from the floor, you can wrap them with a fiberglass batt, and it will help, but it will only slow down how fast they get hot, rather than preventing it.

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