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Thread: Adjust Calcium Hardness before Closing?

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    Join Date
    May 2010
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    Adjust Calcium Hardness before Closing?

    So it's that time of the year again; pool closing. I did a Calcium Hardness check last week, and it was 430!! I have well water that is very hard, but I am surprised it is this hard. I had to refill almost my entire pool in the beginning of the season, then I added chemicals to make it harder.

    Over the hot summer I did have to put the garden hose to it quite a bit, so now it is 430. What do I do now. The pool is being closed in a couple of weeks, and water is being pumped out to be below the inlets. Do I need to do something about it now or wait until the spring. Also, how do you make water softer?

    Thanks!
    24000 gallon Gunnite Pool
    WhisperFlo 1.5 hp Pump
    AquaConfort SWG System
    Solar Heating System

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    Re: Adjust Calcium Hardness before Closing?

    You can't take the calcium out but you can put it in jail so to speak with a sequestering agent. Just about any pool store will carry a scale inhibitor or sequestering agent for high calcium. And I would definitely take care of it before you close it.

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    Mod Squad Bama Rambler's Avatar
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    Re: Adjust Calcium Hardness before Closing?

    Since pool R/O isn't available yet in CT. Your only option to actually lower it is to replace water with low CH water.

    To prevent scaling over the winter you need to get your CSI pretty low so the possibility of it climbing while closed is minimal.

    Use the Pool Calc to adjust things to get it below zero.
    Just for grins and giggles post a full set of test results.
    pH
    FC
    CC
    TA
    CH 430
    CYA
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/hp 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: Adjust Calcium Hardness before Closing?

    CSI will go down as temp goes down, so the risk of scaling over the winter should be on the low side. With a full set of numbers we can be more specific. Next spring you really want to run your well water through a water softener so your refill will help dilute the CH.
    --paulr
    BBB "Intermediate Swimmer"
    IG plaster pool 18.5K gal, Hayward Pro-Grid DE filter, 3/4 HP Hydramax II; Polaris 380, 3/4 HP booster
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    Water testing instructions on one page

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    Re: Adjust Calcium Hardness before Closing?

    The saturation index doesn't go down as much as one might think because as the temperature drops, the pH rises, all else equal. This is because the equilibrium of water with hydrogen and hydroxyl ions is temperature dependent. Going from 85ºF to 55ºF would also have the pH rise from 7.5 to 7.7 so the saturation index only drops by about 0.07 units. Of course, the pH could vary more depending on what goes on with rain water, outgassing, etc.
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
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    Durham, CT
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    Re: Adjust Calcium Hardness before Closing?

    Did a check on the pool yesterday. We got a lot of rain here in the Northeast from the storm, so I had first pump a few inches of water out of the pool. BTW, it is a salt water pool.

    CL - 2 ppm (had my salt system off for a while since the chlorine was very high)
    FC - 0
    PH - 8 (already put muriatic acid in. Its a plaster pool only 2 years old so ph still goes up quite a bit)
    TA - 90
    CH - 380 (a lot lower than the last reading. Maybe the rain water lowed it; or I didn't do the previous reading correctly
    CY - 50

    I also checked my well water CH. It only came in at 150; much lower than I would have thought. BTW, is 150 high for well water??

    I guess a CH of 380 isn't that high and should be OK for the winter?
    24000 gallon Gunnite Pool
    WhisperFlo 1.5 hp Pump
    AquaConfort SWG System
    Solar Heating System

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    Mod Squad Bama Rambler's Avatar
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    Re: Adjust Calcium Hardness before Closing?

    Maybe the rainwater lowered the CH but it would have taken a lot ot lower it that much. Whatever did it, it's a good thing.

    150 CH isn't bad at all for tap water.
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/hp 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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