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freezing of salt water pools


chirpy

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I have a salt water pool which in the past6 years  I HAVE kept pump running during winter in cold spells.

Last year the pump was unuseable probably due to excessive low temperatures and icing -up  and a new one had to be bought.So this year I have drained the pump filter and electrolyser and decided not to run the pumps.

I HAVE A FEW PLASTIC 5 LITRE BOTTLES STRUNG ACROSS THE POOL TO HELP RELIEVE ANY ICE PRESURE ON THE VINYL LINING.

THE LAST WEEK  HAS SEEN VERY LOW TEMPERATURES IN THE LIMOUSIN .I have a winter cover on but removed it today completely as it gives no temperature protection,

My pool has about 1" ice on surface--should I break this up  or leave it????If I break it up WILL  IT  GIVE A LOT OF JAGGED EDGES WHICH MIGHT DO DAMAGE TO THE LINER.?????????????????

What is the freezing point of saline water?does anyone have a table of salinity v freezing point.

I was thinking If I can raise salinity level this will assist/prevent further freezing.

Pool is 4.5x10 metre.

thanks.

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The freezing point depression of water is -1.86C/m.  3000 ppm salt (which in tests really measures chloride and reports the number as ppm sodium chloride) is 0.0513 m which should be doubled since there are separate sodium and chloride ions so the salt only lowers the freezing point of water by 1.86*2*0.0513 = 0.2C.  Ocean water (roughly 35,000 ppm equivalent) freezes at -2C.  In other words, you can't lower the freezing point of the water in your pool enough to make any difference by simply adding salt or any other substance.  It simply takes far too much.  Consider how much anti-freeze needs to be added to water in radiators in order to lower the freezing point.

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[quote user="Ab"]

I have a salt water pool which in the past6 years  I HAVE kept pump running during winter in cold spells.

Last year the pump was unuseable probably due to excessive low temperatures and icing -up  and a new one had to be bought.So this year I have drained the pump filter and electrolyser and decided not to run the pumps.

I HAVE A FEW PLASTIC 5 LITRE BOTTLES STRUNG ACROSS THE POOL TO HELP RELIEVE ANY ICE PRESURE ON THE VINYL LINING.

THE LAST WEEK  HAS SEEN VERY LOW TEMPERATURES IN THE LIMOUSIN .I have a winter cover on but removed it today completely as it gives no temperature protection,

My pool has about 1" ice on surface--should I break this up  or leave it????If I break it up WILL  IT  GIVE A LOT OF JAGGED EDGES WHICH MIGHT DO DAMAGE TO THE LINER.?????????????????

What is the freezing point of saline water?does anyone have a table of salinity v freezing point.

I was thinking If I can raise salinity level this will assist/prevent further freezing.

Pool is 4.5x10 metre.

thanks.

[/quote]

Why panic, you have removed/drained down the pump etc. water expands when it freezes, in the basin of the pool that means it moves closer to the top. This is only a problem if the margelles would be lifted otherwise just let it be, Unless you want to go for a swim [:-))]

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[quote user="Ab"]

I did break it up and removed the cover hoping the sun may melt it a bit-last night it refroze so I WILL LEAVE ALONE AND PUT THE COVER BACK ON.

 

ICE-SKATING WOULD BE POSSIBLE SOON !!!!!!!!!!!!!!!!!!

THANKS.

[/quote]

Bring your skates everyone PARTY at Ab's [:D]

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Intereresting.  We have a saltwater pool, with an abri.  We normally put the winter cover on, but this winter (because we are having a new liner fitted in April) we didn't bother (we did drain skimmers, pump, filter, though).  The lowest temperature I've recorded this year is -7.5, and each day I've wandered out to the pool in trepidation.  Although the condensation on the inside panels of the abri has frozen (with pretty, intricate patterns reminiscent of those on bedroom windows in days gone by!), the water in the pool looks fine, if a little green.

Chris

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We have a pool - not salt water.  It has a security cover and we keep the pump running all winter.  There hasn't been any ice in the pool - not even on the first of the roman steps where the depth is only a cm or two.  The pump is in a box below ground and I have insulated on top.  Lowest temperature of the winter so far is -11C.

 

 

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  • 2 months later...

I also have a salt pool in the Perigord Vert, cant say that temperatures have reached any lower than -5 deg here but I do keep the pump running all winter through, seem to remember that water has its greatest density at -4deg perhaps that stirred up explains why no problem so far also the sub soil here rarely freezes and acts as a heat sink, the wind chill could be an additional factor so keep the cover on.

edit:- sorry water density is greatest at + 4 degC not -4!!!!

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We are in Northern Dordogne, Perigord Vert, and this year was a low of -12 for 2 nights! A few years ago was -14! I always drain the pumps (and remove if Desj. pool or Magiline pools), pipe work etc. Better safe than sorry!

Steve

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Minus 12 deg...gosh I must have been Hibernating then, I'm lucky in that the pump etc are inside the garage, all the pipework is well below ground etc, but I do agree that if you have a pump and pipework at ground level or an above ground pool ie Magiline or desjoyeaux pools it is much safer to drain down, but I notice that the pool experts hav'nt bought me up short on the water density/temperature and sub soil temperatures. Think does the fresh water mains supply freeze to the house?, just trying to provoke a discussion!!!

"Reading another post Re; the cost of ( professionally) winterising a pool; the prices charged (€110 to €410)  and I assume another similar cost to de winterise the pool, seem very close to the cost of a new pump over a couple of years." Discuss. 

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