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Thread: Not closing pool - Freeze question

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    Glock's Avatar
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    Not closing pool - Freeze question

    I am leaving my pool running year round again this winter. My question is, the temps here in Dallas seem to be getting lower sooner this year. This usually means we are in for a cold/bad winter. As long as my pump is running it will be fine right? Moving water can't freeze if I am not mistaken, right?
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    Re: Not closing pool - Freeze question

    Let your pump run when the temps dip below freezing and you should be good. It's gotta get pretty cold for some time to freeze moving water. 😎
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    Re: Not closing pool - Freeze question

    There are countless discussions on this topic in the forum.

    Basically, as long as the water is moving, it would have to be VERY cold (way colder than TX gets) for it to have a chance of freeze damage. Smaller pipes are at higher risk. BUT, if you lose power, then you need to drain the equipment and plumbing ASAP.

    Putting a tarp over the equipment and plumbing can help retain heat and lower the wind chill they are exposed to.
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    Re: Not closing pool - Freeze question

    Quote Originally Posted by Glock View Post
    Moving water can't freeze if I am not mistaken, right?
    Moving water will freeze if the water temp drops below 32* f. The whole premise of the freeze protection in your pool is that the water lower in the pool will be somewhat warmer that the water at the surface. The constant moving of the water will keep it mixed enough to prevent the pipes from freezing. Now, salt water pools will be different. The freezing point of salt water is lower and will vary based on the amount of salt in solution.
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    Re: Not closing pool - Freeze question

    The amount of salt in a SWG pool will not change the freezing point by any meaningful amount.

    I am not sure if I agree your point about the moving water either ...
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    Re: Not closing pool - Freeze question

    I do not profess to be an expert on pool freeze protection. I will say without a doubt however that it is possible for moving water to freeze.

    I was involved with building a new arts center where the lobby had supplemental hot water heating. The GC had not closed in the exterior wall of the lobby, yet he insisted that the hot water system to that section of the building be opened up because moving water does not freeze, especially not hot water. I put it in writing to him that it was possible for it to freeze and insisted he provide written direction before I would open up the hot water run to the lobby - and he complied. Sure enough the pipe burst overnight and I got the early-morning frantic call to stop the water that was spewing into the lobby - the main construction entrance into the building. Enjoyed the I-told-you-so-feeling without rubbing it in his face but did get paid for all the extra work we did to fix it and clean up the mess since I had his directive in writing.

    Here's another one to support the fact that moving water will freeze:

    4 March 2014 - "For the second time in what has been a frigid winter in the Northeastern United States, Niagara falls has come to an icy halt as the six million cubic feet of water that typically flow over the falls every minute has frozen over." (check out the article - there are some awesome photos)

    http://www.dailymail.co.uk/news/arti...low-Falls.html

    I am not familiar enough with the weather in northern TX to say whether or not it gets cold enough there for moving water to freeze. All I'm saying is don't believe that just because water is moving it won't freeze.
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    Re: Not closing pool - Freeze question

    Quote Originally Posted by danpik View Post
    Moving water will freeze if the water temp drops below 32* f.
    Eventually perhaps, but not quickly enough to matter with a swimming pool. It has to go down to around 20 degrees or lower or stay below freezing for several weeks before a pool with the pump running has any significant risk. Even without the pump running there is no real risk if the low is 25+ degrees and the daytime highs are above freezing.
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    Re: Not closing pool - Freeze question

    Right. As Jason said, we are talking about temps dropping below freezing for a few hours overnight ... moving or not, the pool and large pool plumbing pipes are not likely to freeze. An exposed small diameter metal supply pipe for your house is much more likely to freeze in this situation ... and the recommendation always seems to be to have your faucet dripping to keep some water moving in the pipes so the water in the exposed pipe does not get cold enough to freeze solid.

    Now if the temp is dropping below 0 or staying below freezing for days at a time ... then you should not likely be relying on "freeze-protection" and should be closing your pool down properly.
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    Re: Not closing pool - Freeze question

    Quote Originally Posted by jblizzle View Post
    The amount of salt in a SWG pool will not change the freezing point by any meaningful amount.
    True. The statement wasn't meant to be a blanket statement that salt water pools won't freeze. It was simply a CYA as someone would have pointed out that salt water freezes at a lower temp that "regular water". Sea water on average freezes at 28.5* f. So knowing that and the fact that it also has a larger amount of salinity it can be assumed that a salt water in a pool will freeze at a slightly lower temp. What that is, I don't know unless tests are done based on the salinity of the sample.

    Quote Originally Posted by jblizzle View Post
    I am not sure if I agree your point about the moving water either
    Not sure what you are not agreeing with. Water (without additives) will freeze when it gets to 32*, This is Physics 101. Moving or not, once it gets down to that point, it will freeze. Just to clarify, the water has to get to that temp, not the air around it. As for freeze protection on pools, I will stand by my previous comment. The pump running simply keeps the warmer water circulating so the average temp at the surface does not get below freezing by using the warmer water mass that is lower in the pool.
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    Re: Not closing pool - Freeze question

    Quote Originally Posted by JasonLion View Post
    Eventually perhaps, but not quickly enough to matter with a swimming pool. It has to go down to around 20 degrees or lower or stay below freezing for several weeks before a pool with the pump running has any significant risk. Even without the pump running there is no real risk if the low is 25+ degrees and the daytime highs are above freezing.
    I was not disputing that. A question was raised about moving water not freezing. I was simply stating a scientific fact that water, when it reaches a temp of 32* will freeze, moving or not. I am saying the water reaching 32*, not the air temp*.
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    Re: Not closing pool - Freeze question

    Technically, pure water's melting and freezing point is 32F. So in order for water to freeze, all the latent heat must be removed before the water will freeze. This means that the water will remain liquid at 32F for some time before freezing. However, water does not always freeze even when the temperature drops below 32F.

    Water can reach much lower temps (e.g. -55F) before it will freeze. There needs to be a seed (e.g. suspended particle) for ice crystals to form. If the water in the pipes is very still, then they may not freeze until the water is disturbed (i.e. pipe is hit). Should the water temperature reach 32F or below, it may actually freeze faster when moving then when completely still because of this phenomenon. But before the water reaches 32F, it is much better to circulate the warmer water from the pool through the pipes.

    Here is a good visual for super-cooled water:

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    Re: Not closing pool - Freeze question

    I have had this happen to my beer
    Opened up a super cold Corona and as soon as the first drop of lime juice entered the bottle ... the entire beer solidified
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    Re: Not closing pool - Freeze question

    Quote Originally Posted by jblizzle View Post
    I have had this happen to my beer
    Opened up a super cold Corona and as soon as the first drop of lime juice entered the bottle ... the entire beer solidified
    That's what came to mind while watching that video. Beer-sickle.

    For the past 3 years I have been leaving my pool open year-round after one year of fighting with trying to tarp it.

    Last year during the worst cold spell my pipes never froze and my pool survived. For 3 nights the air temp bottomed out just above 10 F and day temp was at or below freezing. At day 3 or 4 I had over 1/2" of ice on the pool surface. I kept the pool water level near maximum so that the ice didn't lower near the intake and had my suction cleaner going so that even if the skimmer froze up water could still flow from the pool bottom.

    Of course I kept my pump on continuously during this period.

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    Re: Not closing pool - Freeze question

    I'm there right now.
    We bought our home with an IG pool and the previous owner has been great about helping with the stuff he built or installed, which is basically everything. In exchange, I'm letting him store a lot of stuff in the out buildings until he gets his new place finished. Not a bad deal for either of us. (I couldn't fill them in my life time)
    Anyway, he has assured me that he will help me close the pool when the time is right. We've been below 32 for a week and we set a record low of 8 deg F a couple of nights ago. I've been running the pump 24/7 for a week until this morning. I have not had any freeze problems.
    I would like to close very soon, maybe this weekend. This discussion explains to me several of my concerns about freezing.
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    Re: Not closing pool - Freeze question

    If you want to get technical: Water is complicated. There are a whole bunch of things going on. The dominant effect is that the bulk pool water is typically above freezing and has a much slower cooling rate than water sitting still in the pipes. Keeping the water well mixed by running the pump keeps the water in the pipes above freezing despite the higher cooling rate in the pipes compared to the bulk pool water by spreading out that cooling across the bulk pool water.

    But there are several additional effects that don't tend to be significant around pools, but do make any "absolute" answers wrong more often than not. The simplest effect is that it takes time for water to freeze. While that is happening, the frozen water typically stops moving. So it isn't so much that the moving water doesn't freeze, instead it is that the not yet frozen water keeps moving.

    There is also heating caused by the movement/friction of the water. This effect is very small, but can be enough to keep moving water from freezing despite the environment being below freezing, at least as long as the temperature differential isn't all that high.

    It is also possible for the required nucleation sites to get preferentially removed from the moving water, allowing the moving water to become super cooled. This effect often occurs in fast moving mountain streams, allowing them to be below 32 degrees and not freeze (i.e. super cooled). In these situations, freezing still progresses from the outside in, so that the stream will eventually freeze solid, but this can take some time, potentially several weeks if the conditions are just right. One effect that enhances this one is that ice is a good insulator, so the outer layer of ice slows the cooling rate of the moving core by reducing heat transfer to the environment.

    There will also be water that never freezes due to differential concentration of impurities. As the bulk water freezes, impurities become concentrated in the remaining liquid water, eventually accumulating enough to lower the freezing point below the ambient temperature in nearly any plausible situation. This has dramatic effects on polar ice sheets, as life becomes concentrated in the remaining liquid water, which tends to form channels that allow far more movement and ongoing development of that life than most would expect in polar conditions.

    But none of that really matters in swimming pools, where all you need to know is that running the pump does indeed prevent freezing of the water in the pipes for a time, but not forever. There is a whole band of moderate climates where it does freeze, but the amount of time you gain by running the pump is long enough that spring comes before there is any problem. At least as long as the power doesn't fail.
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    Re: Not closing pool - Freeze question

    I left mine open this year. Since it was really cold this week I left the pump running and covered the exposed pipes with heat tape. Last year it was a huge pain getting the cover on then it got holes in it and sank anyway. Leaves got in under the cover and it was a mess. This year l decided not to cover and leave everything open. I run the cleaner if it's sunny or warm enough and clean up any leaves on the bottom. Dump in a gallon of bleach every few days and so far so good.

    Hope all is going well with your pool!
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    Re: Not closing pool - Freeze question

    Quote Originally Posted by danpik View Post
    I was not disputing that. A question was raised about moving water not freezing. I was simply stating a scientific fact that water, when it reaches a temp of 32* will freeze, moving or not. I am saying the water reaching 32*, not the air temp*.
    Science is not that simple. Super pure water can go way below 32 degrees without freezing if there is absolutely no movement. I believe that you can get as low as -50F.

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    Re: Not closing pool - Freeze question

    Quote Originally Posted by 1380ken View Post
    Science is not that simple. Super pure water can go way below 32 degrees without freezing if there is absolutely no movement. I believe that you can get as low as -50F.
    Well, it is -40 and as long as you do not provide any nucleation sites, I will agree. However I doubt that a pool will ever be that pure and the simple act of running the pump will create the needed nucleation sites to cause the freezing.
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    Re: Not closing pool - Freeze question

    Im no expert but living in Maine I watch the Kennebec River freeze every year.... Tidal water as well as a flowing river. Yes it does freeze!!

    Side note, tidal water that freezes at high tide... tide goes out, river sinks down to water level, then goes back up as tide comes in. Coolest thing in the world to see


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