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Thread: Pool closed for the winter...pH keeps rising

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    Pool closed for the winter...pH keeps rising

    I had some horrible scaling issues when I opened the pool last year, supposedly due to the new plaster causing the pH to rise over the winter. This year when I closed it, I ensured that the pH was down around 7.1, and I also added a couple of jugs of ScaleTec in the hopes that it sitting in there with a low pH over the winter might eliminate the need for me to have the pool acid washed next year. I peeled the pool cover back yesterday and took a pH measurement (it's been about a month since I closed), and to my surprise, the pH was off the charts! Obviously this is not going to help my chances of not having to acid wash. Anyway...my questions are this:

    1) What can I do to drop the pH when the pump isn't able to be run?

    2) Why is the pH rising so much and so fast? I'm starting to wonder if there isn't an issue with the plaster/Diamondbrite job. Is it possible that my pool builder did something wrong that is causing the pH to rise, or is this a normal occurrence?

    Any help is greatly appreciated!!

    Thanks!
    25,000 gallon IG gunite pool with Diamondbrite finish built May, 2012
    All Pentair equipment:
    FNS Plus 48 sq. ft. DE Filter, 1 HP SuperFlo Pump, IntelliChlor IC40 SWG, MasterTemp 400k BTU/HR Heater, Prowler 820 Vacuum
    Test Kit - TF-100

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    linen's Avatar
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    Re: Pool closed for the winter...pH keeps rising

    Can you post your last full set of test results (and when you got them)? especially: TA, CH, ph, cya, salt (if used), borates (if used)

    Ph will go up as temperature goes down, though yours sounds excessive for that.
    TFP Expert who uses Pool School and my TF100 test kit along with PoolMath for my: Round 11K gallon AGP with deep end, 20" sand filter, Matrix 1hp 2spd, 6 2ftX20ft solar panels (and solar cover!), Intex SWCG (copper bars disconnected) and a Rubadub hot tub (chlorine). The SLAM process is not finished until: 1. CC < 0.5 ppm, 2. An OCLT < 1.0 ppm and, 3. The water is crystal clear.

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    Re: Pool closed for the winter...pH keeps rising

    Last full results were taken on the evening of September 19th, and the pool was closed the morning of the 20th. Here they are:

    FC - 13.0 (I had shocked and let drop back down about half way as described in 'Pool School')
    CC - 0
    pH - 7.2
    TA - 90
    CYA - 70
    CH - 320
    Salt - 3050
    Water Temp - 73 F
    Filter Pressure - 15
    25,000 gallon IG gunite pool with Diamondbrite finish built May, 2012
    All Pentair equipment:
    FNS Plus 48 sq. ft. DE Filter, 1 HP SuperFlo Pump, IntelliChlor IC40 SWG, MasterTemp 400k BTU/HR Heater, Prowler 820 Vacuum
    Test Kit - TF-100

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    Re: Pool closed for the winter...pH keeps rising

    Linen: Any suggestions?

    25,000 gallon IG gunite pool with Diamondbrite finish built May, 2012
    All Pentair equipment:
    FNS Plus 48 sq. ft. DE Filter, 1 HP SuperFlo Pump, IntelliChlor IC40 SWG, MasterTemp 400k BTU/HR Heater, Prowler 820 Vacuum
    Test Kit - TF-100

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    Mod Squad Bama Rambler's Avatar
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    Re: Pool closed for the winter...pH keeps rising

    I'm not Linen, but if it's rising that much that quickly you could drop a sump pump in the pool to circulate the water and add some acid to keep the pH in the 7's.
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/¼hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
    Pool School ----- Pool Math ----- TF-Test Kit

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    Re: Pool closed for the winter...pH keeps rising

    I don't know anything about closing pools, but does the fact that the water was still in the 70's when the pool was closed have any effect on what is happening? I would think it would have been best to let the water drop into the 50's and then adjust the water at that time to help the pH from rising so much.

    I would do as Dave suggested, get a sump pump and acid in the water.
    16k gal plaster with raised spa, Jandy DEV60 filter, 2 HP 2-speed SHPF Jandy Stealth pump
    Hayward Aqua Rite T-15 SWCG, Jandy LXi 400k BTU NG heater, 350 sq.ft. of Sun Star solar panels, TF-100 Test Kit, Dolphin s300i Cleaner
    Test Kits . Pool Math . Chlorine/CYA Chart . The SLAM Process

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    linen's Avatar
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    Re: Pool closed for the winter...pH keeps rising

    The comments you got by Bama and ping are good!

    Since you have had scaling in the past you should probably get familiar with Calcite Saturation Index (csi) if you are not already. The csi is a measure of potential for pitting (csi low) or scaling (csi high) and is a function of ph, TA, CH, cya, salt level, borate level, and water temp. When you took those test values above (and assuming ~80F pool water temperature and borates close to 0), the csi was okay but was on the low side (towards risk for scaling but still in the "safe" zone) at -0.5 ("safe" range is between -0.6 and +0.6). So even if your ph goes up to 8.2, your csi will only go up to +0.15 when the pool water temperature is 50F and actually won't reach +0.6 csi (the start of risk for scaling) until your ph goes above 8.7. Additionally, scaling/pitting occurs at a much slower rate when the water temp is cold.

    Bottom line, I don't think you are at much danger for scaling, but since you have experienced it over the winter in the past and the fact that the ph test kit does not measure above 8.2, you are probably safest to keep ph measurable on your test kit at or below 8.0 (but not below 7.4) using the method that Bama suggested.

    Here is the pool school article on csi: http://www.troublefreepool.com/pool-...alcium_scaling
    TFP Expert who uses Pool School and my TF100 test kit along with PoolMath for my: Round 11K gallon AGP with deep end, 20" sand filter, Matrix 1hp 2spd, 6 2ftX20ft solar panels (and solar cover!), Intex SWCG (copper bars disconnected) and a Rubadub hot tub (chlorine). The SLAM process is not finished until: 1. CC < 0.5 ppm, 2. An OCLT < 1.0 ppm and, 3. The water is crystal clear.

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    Re: Pool closed for the winter...pH keeps rising

    Thanks for all the info...I will definitely get some acid in there and circulate with the sump pump. How long would you say I need to run the pump for?

    Also, the real question here is why am I having this issue? Is there something with regards to how the Diamonbrite was put in that is causing this? Is it an issue to push with my pool builder, or is this just par for the course?

    Thanks!
    25,000 gallon IG gunite pool with Diamondbrite finish built May, 2012
    All Pentair equipment:
    FNS Plus 48 sq. ft. DE Filter, 1 HP SuperFlo Pump, IntelliChlor IC40 SWG, MasterTemp 400k BTU/HR Heater, Prowler 820 Vacuum
    Test Kit - TF-100

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    linen's Avatar
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    Re: Pool closed for the winter...pH keeps rising

    Normally we say circulate for at least an hour after adding chemicals, but since the sump likely moves less water, I would probably run longer...maybe 2 hours.

    How old is the plaster? Usually after a year, ph rise from new plaster will go away.
    TFP Expert who uses Pool School and my TF100 test kit along with PoolMath for my: Round 11K gallon AGP with deep end, 20" sand filter, Matrix 1hp 2spd, 6 2ftX20ft solar panels (and solar cover!), Intex SWCG (copper bars disconnected) and a Rubadub hot tub (chlorine). The SLAM process is not finished until: 1. CC < 0.5 ppm, 2. An OCLT < 1.0 ppm and, 3. The water is crystal clear.

  10. Back To Top    #10

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    Re: Pool closed for the winter...pH keeps rising

    The pool was completed in April, 2012. Should I still be having these issues? And would it be to early to acid wash the pool next spring? I'm worried that if I do, I'll just have scaling again next winter.

    25,000 gallon IG gunite pool with Diamondbrite finish built May, 2012
    All Pentair equipment:
    FNS Plus 48 sq. ft. DE Filter, 1 HP SuperFlo Pump, IntelliChlor IC40 SWG, MasterTemp 400k BTU/HR Heater, Prowler 820 Vacuum
    Test Kit - TF-100

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