pH after closing

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ulrichsd

ulrichsd

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May 19, 2014
97
Cincinnati, OH
Just had my pool closed 2 weeks ago (by the company that did my remodel) for the first time as an owner, after refinishing the pool this spring.

They lowered the water below the returns, aired out the lines, added antifreeze to the pipes and an algecide to the water. I have been adding chlorine once a week at least until it gets down to freezing.

I must have either overshot dropping my pH (the new plaster has continually raised the pH all summer so i had to add MA about every other week) or maybe the algecide lowered it, and now it is down to about 6.6.

My question is, will that hurt anything if i leave it as is? Or should I bring the pH up? I'm guessing it will creep up before spring anyway...

It's a 20×40, about 30,000 gallon plaster pool. Here's my numbers:
Cl: 3 ppm
CC: 0 ppm
ph: 6.6
TA: 80 ppm
CH: 200 ppm
CYA: 30 ppm
Water temp: guessing around 55 F

A pool calculator app lists the CSI at -1.0, not sure if I should worry about this while the cover is on and no one is swimming...

Thanks for the help! Any other tips for winter maintenance are appreciated as well!

Thanks,
Scott

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Well, being that low with fresh plaster is not good. Being covered means the water won't outgas any CO2 which means the pH won't creep up very fast.

Your only option for fixing this is to try to add some borax, pre dissolved in water, and a submersible pump to agitate it. Given the size of the pool, you probably need two pumps.

Others with more winter closing experience will have to chime in.


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Thanks, I'll raise the ph back up to 7.2 or so and maybe boost the TA as well. Playing with the calculator shows me what a big effect lower temp has on decreasing CSI pretty quickly.

I should have noted that he said they added something to help prevent scaling as well and i bet that may have reduced the pH also.

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Checked pH tonight and it was up to 7.8-8.0 range, looks like i overshot a bit. TA was 100. That's a CSI of 0.1 at a temp of 55 F.

With the pool drained to below the returns it's probably more like 20,000 gallons.

I'll drop in just a little acid tomorrow to get it closer to 7.5ish? Or maybe I m ok with it for now since CSI is close to 0?

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My calculator says CSI = -0.1 at pH 7.8 and 55 deg. But CSI would be -0.3 when the temp drops to 40 deg.

If I lower the pH to 7.5 the calculator says CSI would be -0.6 at 40 deg.

How much should I worry about low CSI during cold winter months?

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If you leave your pH where it is, you should be ok. Why would you lower your pH to 7.5? If you are closing this pool, then either raise the TA or pH so that you water stays balanced even when it is cold out. You can assume your water temperature won't get much lower than 32F so that would be the worst case scenario.

CSI is just a parameter that tells you the degree to which the water is saturated with calcium carbonate. 0 CSI means the water is perfectly saturated. Positive CSI is oversaturated and negative CSI is under saturated. What the CSI DOES NOT tell you is if or when scaling or etching will occur or at what rate those processes will occur. It is entirely possible to have a positive CSI over 0.6 and not get any scaling because there is nothing to initiate the process. Likewise, even if your water has a negative CSI, the rate of etching is so slow that it doesn't matter.
 
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