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Thread: The Physics of Freezing and Freeze Protection

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    Re: The Physics of Freezing and Freeze Protection

    Hello, I'm a new IG pool owner in NJ where we've been having below freezing temperatures at night AND daytime for a couple of weeks now with finally a break from freezing temps this week. Our pool is covered with a polycarb structure and we've been running the filter 24/7 during this time as well as heating the pool to 90F when we want to swim in it. The pool water gets down to the lowest of 65F in between heating/pool use. We also have freeze protect mode set at 34F.


    In deciding whether we want to keep the pool open in future winters, we need information about when pipes freeze and burst to ascertain the risks we want to take in exchange for being able to swim in NJ winters.

    More specifically, if our filtration system breaks or loses power:

    1. First, is there any risk of below ground pipes freezing?

    2. Is the risk more for the exposed pipes connecting to the equipment (vs underground pipes) that could be resolved if we build a shed over it or put foam around the exposed pipes, etc. ? I think the information referenced above about time to freeze refers to pipes located above ground, perhaps that at the equipment? My pipe is PVC and 2".

    In deciding whether to keep our pool open for future winters in NJ, the main risk is should our filter stop running due to it breaking or losing power, will we have enough time to fix it before the pipes could freeze and burst. I know no one knows the exact answer of when this could happen b/c there are multiple variables as referenced above.


    However, I'm just wondering if I have ENOUGH time to fix the motor BEFORE pipes burst. If the pipes could freeze in a matter of a few hours, then maybe we should close our pool during the NJ winter months of Dec-Feb. since we won't have time to repair before the damage occurs (like when it stops running in the middle of the night unbeknownst to us)

    If it takes like 20-30 hours for the pipes to freeze, then I can keep our pool open during the long freezing temps of NJ winters and minimize our risk by buying an extra motor to have on hand and possibly putting our filter on backup on our whole house generator (don't know if I can yet depending on how much power it uses)

    I appreciate any thoughts on this. Thanks.


    Phuong in NJ



    16" x 33' concrete wall vinyl liner IG pool, Jandy CL340 cartridge filter, Jandy 2.0 HP pump, Jandy JXi260 natural gas heater

  2. Back To Top    #22
    mas985's Avatar
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    Re: The Physics of Freezing and Freeze Protection

    1. Yes but it takes a lot longer for pipe to freeze underground vs above ground. You can prevent freezing all together underground if the pipe is buried deep enough to be below the frost line. However, the pipe going from above ground to underground is still vulnerable.

    2. Yes and yes

    Should power fail, the above ground plumbing will freeze first and the time to freeze is dependent on several variables. Draining the pad equipment can extend the time to freeze by quite a bit plus if there is air in the pipes for the ice to expand, even if the remaining water does freeze, it is unlikely to do any pipe damage. It is only when the ice expansion is constrained, that you can have pipe damage. So leaving all flow valves in an open position can also help.
    Mark
    Hydraulics 101; Pump Ed 101; Pump/Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, MaxFlo SP2303VSP, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

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    Swampwoman's Avatar
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    Re: The Physics of Freezing and Freeze Protection

    Hi phuong. I can't answer your question but have certainly tried to figure this out for my own purposes

    I am running in Michigan (in an air dome) with similar concerns.
    During the "deep freeze" before Xmas, my heater quit and I do not have a bypass. But since I keep my water in the 90-95 range and since my pump was still running, I was okay for the net four days it took to diagnose, ship the part and replace the heat exchanger (heater is indoors in a pool house.) In this scenario, my water temp did ultimately drop to high 70s over that time. The speed of drop slowed considerable as the temp lowered in the pool.

    For the pump, I chose not to take any chances, so do have a single speed backup motor on hand in the event of failure and a shaft seal kit. I had upgraded to a vsp motor this summer while my existing pump was still functional with this in mind, and also "learned" how to change the motor so that I would know how under duress to do this meant retrofitting a vsp motor instead of getting a whole new pump as I wanted the motors to be swappable in emergency.

    For power outages, which I have had, I now run a 10k Generac gc (contractor style portable, not whole house, but good overhead) to the pool house and house. From the generator I was able to handily operate the pool pump, heater, chlorinator, house well pump, boiler pump and a few dedicated circuits for several days (and several gallons of gas

    Ymmv, but in my case I just decided that operating in winter was worth the precautions -- in my case I'm using the pool for a physiotherapy routine that helps keep me mobile despite arthritis in my knees and a replacement in my future. That meant having an electrician install an interlock kit to safely operate the generator, plus the cost of the generator. Our major, multi day outage was less than a month after this move, so it certainly felt like the right route

    Btw, I have enclosure envy I'd love what you have but my footprint was a bit too irregular to make one of those work!
    In ground extended Grecian, 22,000 gal, Hayward 220t sand filter, vinyl liner, dolphin m4 supreme.
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  4. Back To Top    #24
    Swampwoman's Avatar
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    Re: The Physics of Freezing and Freeze Protection

    Is the risk more for the exposed pipes connecting to the equipment (vs underground pipes) that could be resolved if we build a shed over it or put foam around the exposed pipes, etc. ?
    Is your equipment pad outdoors? Or are you talking about pipes that run out and then into the ground?

    My equipment is in a pool house, but the exposed pipes come out of the pool house for a few feet and then go underground. We built a box with thermax foam insulation inside and put a temp monitor in there. Since we keep the pool warm, the pipes and air inside the box also stays warm.

    If your equipment is out of doors in particular, operating in winter may negatively affect your heater because the extremely cold intake air can cause condensation that is then highly corrosive as the condensate of combustion accumulates and soots your heat exchanger. If its possible to build a heated enclosure, this would protect your heater better, but note that you need at least an inch of makeup air venting for every btu...eg my 266k heater needs 266 square inches of intake venting for makeup air for proper combustion.
    In ground extended Grecian, 22,000 gal, Hayward 220t sand filter, vinyl liner, dolphin m4 supreme.
    If TFP has helped you, please click to SUPPORT TFP!
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