Thread: What min temp & for how long before water systems freeze

  1. #1
    Join Date
    Jun 2009
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    Default What min temp & for how long before water systems freeze

    Any practical experience with what "minimum outside temperature" and for "how long (exposure)" can a camper be subject to low temperatures before you can expect problems with underbody external water tanks (plastic) or pipes (plastic) freezing?
    Water pump is inside the camper, so is OK. Inside has Webasto DualTop heater/HWS. Thetford toilet is also inside.
    I realise water freezes at 0 deg C (32deg F) but a 100 litre water tank isn't going to freeze immediately.
    E.g. if overnight temperatures are below freezing, but daytime temps are above freezing, and average temp over 24 hours is also above freezing, can I assume water systems would be OK?
    Are there any good threads or links that provide advice on "winterising" a camper's water systems.

  2. #2
    Join Date
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    Very complicate subject that I have experience in but no empirical data. I've lived at 1525 meters for over 25 years so I have lots of freezing experience. Large volumes like water tanks have a lot of thermal mass, and the process of freezing gives off heat so in a closed space they are fairly problem free.

    The issue is with items with low volumes of water like water pumps and narrow pipes. These freeze up quickly and usually result in expensive repairs.

  3. #3
    Join Date
    Nov 2007
    Location
    West Texas
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    Try this for some general winterizing information.
    http://www.fiberglassrv.com/winter.html
    Most RV sites will have info about winterizing and/or cold weather operation
    Last edited by DontPanic42; 11-14-2010 at 01:40 PM. Reason: Add comment
    Bruce
    '04 Mitsu FUSO FG639 / '04 Casita
    aka:"RoadHippo"
    West Texas
    " 200 miles from everywhere!"

  4. #4
    Join Date
    Feb 2009
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    NSW Australia
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    In Germany I had the grey tank freeze up overnight when the minimum temperature was about -8C. Daytimes were above freezing - about +8C. No wind to speak of.

    Too many factors to be too specific. Wind makes a big difference. Amount of insulation is a big factor in delaying but not preventing freezing.

    Usually it is the water pipes that freeze first and if they are protected, can stay frozen for a long time. I had the pump suction line freeze even though everything was inside and in a well-heated MH. It ran hard against an uninsulated plastic wheel arch, and was jammed between that and the insulated side wall. Even when the temperature outside rose well above freezing, the pipe stayed frozen and late in the afternoon I had to dismantle part of the cupboards to find it. All the other pipes were routed well clear, except for this one. Easy fix one I got to it.

    Grey tank stayed frozen all day and I had to resort to pouring heaps of salt down the sink before I could empty it.

    Steep learning curve for an Australian in the middle of an European winter - even though the MH was supposed to be winter rated with double floor etc.
    Tony LEE
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  5. #5
    Join Date
    Sep 2009
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    Australia
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    Central Plateau, Tasmania, early April 2006.
    One night, not really cold.

    The only water we had in the morning to make the coffee with was in the fridge.
    Water was frozen in the outside plastic pipes (John Guest). No damage was done and they thawed fairly quickly.

    Cheers,
    Peter
    ......................Enjoy.....................
    OKA196, 4x4, DIY, self-contained motorhome. http://www.oka4wd.com/xt196.htm

  6. #6
    Join Date
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    Quote Originally Posted by Martyn View Post
    Very complicate subject that I have experience in but no empirical data. I've lived at 1525 meters for over 25 years so I have lots of freezing experience. Large volumes like water tanks have a lot of thermal mass, and the process of freezing gives off heat so in a closed space they are fairly problem free.

    The issue is with items with low volumes of water like water pumps and narrow pipes. These freeze up quickly and usually result in expensive repairs.
    Yup freezing is exothermic, it warms up the surrounding areas. So a lot has to do with the ratio of surface area to volume. Kind of like what the guys said above - a skinny long pipe freezes quicker than a short fat pipe that both contain the same volume of water. There is a rough number that includes normality(# of particles dissolved in water) ratio of surface area/volume, Temperature and specific heat of the solvent.

    -Sam
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