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Thread: Pressure relief valve to reduce pipe bursting?

  1. #16
    Forum Admin, Expert Plumber Terry's Avatar
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    Aug 2004
    Bothell, Washington
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    What I actually do when I'm gone for two weeks, is leave some heat on, and the water.

    I suppose a smarter thing to do would be to turn off the water too, and the gas to the water heater. I can alway relight when I get back.
    Normally though, unless there is a power outage, you're going to be okay.

    I have seen burst washer hoses that overnight put three inches of water in a basement.
    I've seen a neighbors water heater go bad to the point that it ran down the hill to the home below them, and the river of water went into that home and caused damage.
    I've seen the home with nine pipe splits. They were in California for the Winter and turned off all of the heat.
    And tons of frozen pipe splits during our power outages around here in Winter.

    On the hot water side freezing quicker. There is science behind that one. Though I find that observation will tell you it's happening on the hot side more, and if you ask around, there are text book types that will know the reason why. For the plumbers, it just gets drilled into you, as often you are repairing the hot side, and the cold side is okay. Two pipes side by side, one is split.

    For years we knew a day was 24 hours by observing it. Once day we realized that the earth was spinning. That was science. Sometimes it takes a while to catch up to each other.
    There was a time when science thought the world was flat.

  2. #17
    Moderator & Master Plumber hj's Avatar
    Join Date
    Aug 2004
    Cave Creek, Arizona


    quote: .. are they all wrong? Also, if we keep the faucets running, it seems to me they have to go almost full blast in order to prevent freezing since introducing 34 degree water at a drip or trickle is in no way effective in keeping a 10 degree hosebib from freezing. Anyone that's ever turned on the cold water faucet during cold weather knows how cold that water is... if it's not in the 30's,

    1. YES! Unless you are misinterpreting what they state.
    2. It only takes a small amount of flow to dissipate the chilled water.
    3. When you turn on a "cold faucet" in the wintertime, it may be cold, but it is NOT 32 degrees. And since cold water has entrained air and other "minerals", it freezes below 32 degrees, but hot water has that "stuff" precipitated out during the heating process so it WILL freeze at close to 32 degrees, which is why it WILL freeze sooner than cold water. If the heater is on "vacation" or any other operating temperature, it will NOT be able to cool down to the freezing point so you do not have to drain it, but if it is completely shut off, then it should be drained or it WILL freeze and deform, if not rupture.
    Licensed residential and commercial plumber

  3. #18
    Retired Defense Industry Engineer jadnashua's Avatar
    Join Date
    Sep 2004
    New England


    Hot water tends to get any entrapped air stripped out of it, and sometimes minerals, so the water is purer. Just like salt lowers the freezing temp, making the water purer can get it closer to 32. There are two ways to ensure you don't get frozen pipes: keep the heat on, or drain the water which may mean using an air compressor to purge the pipes. If you are living there, and you have pipes running in unconditioned space, that's a big problem. Insulation does not generate heat, it slows the movement of it. IF there's none there in the first place, it can't do much. All it takes is one little air leak on a windy day, no water flow, and a spot can freeze since the moving air moves away any heat that's there more quickly. Where it gets below freezing on a regular basis (and not a bad idea elsewhere, too), it's bad practice to run water pipes in an outside wall if they could have been run in an inside wall. It's a good idea to check any new house. People like to put sinks by a window. In that case, it can work better (from a freezing viewpoint) to bring them up into the cabinet from below, rather than out from the wall. Another tip - if you do have any on an outside wall, overnight, you may want to open the cabinet doors which will allow some of the room heat to keep it warmer there.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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