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Thread: PH Drop over the winter months

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    Catanzaro's Avatar
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    PH Drop over the winter months

    It is nice to be back on the forum. Opened my pool a few days ago and my PH level has dropped from 7.5 to 6.8 during the winter months (may be even less based on kit). I added the remainder of Borax to raise the PH. Last year, my TA was at 120 and I managed to bring the level down to 100 (prior to closing). Because I had constant rising PH levels (requiring acid additions every 4 days), I decided to pump the winter water on the cover back into the pool. It appears that the TA has dropped to around 70. Will test again tomorrow.

    At moment,
    TC = 8
    CC = 0
    CYA = 50
    TA = 70
    CH = 175

    With the PH being at 6.8 or even 6.6 (not sure), does this pose any threat to the liner, corrosion and staining? It is real important to bring the PH back up quickly, or should I aerate and bring up slowly? Please advise!
    14,700 gallons IG Pool Vinyl Liner - Octal Circulation System
    Hayward Pro-Series 350 LB. Sand Filter Model # S270T - 2" Plumping
    Hayward CL2002 Chlorinator - Hayward Super Pump 2 HP Model # k48m2n111
    Hayward AQR9 SWG 25K Salt Cell & TF-100 Test Kit + Speed Stir
    Gulfstream HE125RA - 117K BTU Heat Pump - Date of Build is 11-2013

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    Mod Squad JVTrain's Avatar
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    Re: PH Drop over the winter months

    Low pH can cause damage the most quickly to your heater, if you have one. It can leach copper from the heater element, damaging the element and putting copper in your pool. That's the only risk you might have for staining but that's a bad one. I would use some borax to get the pH up, targetting 7.0 while doing some aerating if you have a method for doing that. Yes, borax will add some TA back to your pool but not much and it's worth it to get the pH up into range. Acidic conditions can make your liner more brittle as well if left that way for long periods, iirc.

    I was surprised that my pH was low as well when I opened but only 7.2 to 7.4, not below the scale like yours. What's your water temp?
    Joel - TFP Moderator - Minnesota - **Become a TFP Supporter!** Helpful Links: ABCs of Pool Water Chemistry - SLAM Procedure - Chlorine/CYA Chart
    40x20 Pool: 32K Gallons * Vinyl * Bleach Chlorination * Hayward S270T Sand Filter * Pentair SuperFlo 1 HP * Teledyne/Laars Heater * AquaVac Tigershark * TF-100 w/ SpeedStir
    Isolated Spa - 345 Gallons

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    Catanzaro's Avatar
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    Re: PH Drop over the winter months

    I do not have a heater (so far so good). Heading to purchase a box of Borax. The water temperature is 54 degrees. A lot of water from the winter was pumped back in the pool and that is what probably lowered the PH. Each year, the PH drops within a month of closing (do not know why). More concerned about liner and screws around light niche. Had an issue with rusty screws, but this has been fixed with the assistant of Chem-Geek and a sacrificial zinc anode at the pump.

    Just tested water and it appears that the PH is at 7.2. Will leave as is for now and if does not change within one week, I will add more Borax. I have 8 returns, 4 are oscillating, which create a lot of aeration. With the lower TA, this could be the pool's sweet spot.
    Last edited by Catanzaro; 04-28-2016 at 06:46 PM. Reason: Tested water at 7:30 p.m.
    14,700 gallons IG Pool Vinyl Liner - Octal Circulation System
    Hayward Pro-Series 350 LB. Sand Filter Model # S270T - 2" Plumping
    Hayward CL2002 Chlorinator - Hayward Super Pump 2 HP Model # k48m2n111
    Hayward AQR9 SWG 25K Salt Cell & TF-100 Test Kit + Speed Stir
    Gulfstream HE125RA - 117K BTU Heat Pump - Date of Build is 11-2013

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