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Thread: Testing in Colder Water

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    Join Date
    Aug 2012
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    Testing in Colder Water

    I have a new pool (filled in August 2012) and this is my first winter (as much of a winter that we have in Houston). My question is, which tests work well in colder water (upper 40's to low 60's) and which tests need the water to be around 70 or higer? I think I have read somewhere on here that the CYA test works best with water temps of 70 or higher, but I don't see anything on the other tests.

    For the tests that need the water warmer - what is the best method to warm it up? I am guessing to just grab a larger sample from the pool and then placing that sample in a warmer water bath - but if I do this, how much time do you have after taking the sample from the pool before the tests might be off?


    I have a TF100 kit with a plaster pool.

    Thanks,

    Steve
    20,000 IG WetEdge Satin Matrix Northshore Plum, Filled 8/24/12

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    JasonLion's Avatar
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    Re: Testing in Colder Water

    Only the CYA test is prone to errors due to cold temperatures. It is important to do the PH test fairly quickly, while the water is still at it's original temperature. The FC test is also time sensitive. It doesn't care about temperature so much as time passing between taking the sample and performing the test. The other tests can sometimes take a little longer to mix or to settle to their final color when the water is cold, but will work at any temperature above freezing and up to a little above spa temperatures. For the CYA test, I just leave the water sample sitting on the counter indoors for an hour or so and then test the CYA level.

    Another think to keep in mind, only slightly related to your question, is that you want the PH to be higher when the water is colder. Water down below 40 degrees should have it's PH be around 0.4 higher than it would be at swimming temperatures.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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    ComputerGuyInNOLA's Avatar
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    Re: Testing in Colder Water

    Jason,

    Why do you want the PH to be higher in cold water? Just curious. My pool is about four months old and it is a constant battle with PH due to water falls, new plaster, and a SWCG. Can I let is rise higher when it is cold without damaging new plaster?

    Thanks,

    David Hurley
    Gunite/Plaster pool at 13k gallons. All Jandy with CL340 series cartridge filter, 1.5 HP Jandy Stealth pump. Jandy 1400 SWCG and PDA4 controller. Dual waterfalls. Polaris 280. Pool installed August 2012. Southern Louisiana. And lets not forget my trusty TF100 test kit!

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    JasonLion's Avatar
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    Re: Testing in Colder Water

    Most people have no reason to think about this. The pool is normally closed in the winter and 99% of the time the PH adjusts it's self naturally as the temperature shifts, without any effort on your part.

    However, if your really want to know Higher PH in cold water compensates for the CSI being lower when the water is colder. You can play with the temperature numbers in the Pool Calculator to see how this works. Normally you don't need to think about this, as the PH will rise naturally just the right amount as the water gets colder, and drop again as the water warms up. However, fresh plaster can occasionally upset that balance as it raises the PH regardless (though not anywhere near as quickly when the water is cold). If you are keeping the pool open through the winter and managing the PH, you need to be aware of the natural PH shift, so you don't accidentally bring the CSI down too low and cause plaster damage while the water is cold.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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    Mod Squad jblizzle's Avatar
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    Re: Testing in Colder Water

    I think this finally eases my feelings ... having recently just lowered my pH in cold water. I was looking at the CSI when I chose my pH target, and wanted to ensure it read slightly negative over winter ... since I was targeting 7.2 I was a bit worried after seeing these posts. But given all the other parameters, I guess I should be fine.

    Posted from my Droid with Tapatalk ... sorry if my response is short
    Jason, TFP Moderator
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