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Thread: Lower calcium hardness?

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    Join Date
    Mar 2015
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    Lower calcium hardness?

    My K-2006 test kit finally arrived today so I ran a test on my water. Here are the results:

    FC - 0.8
    pH - 7.5
    TA - 70
    CH - 425
    CYA - 35

    I've had a floating puck dispenser in the pool for the last couple weeks until I could test the water, since I had no test kit before today. Obviously FC was way low, so I just brought it up to 14 with bleach to start a SLAM procedure. My main concern is the calcium hardness at 425. I measured the tap water at 190, so the calcium didn't come from there. We just moved into the house 3 weeks ago, so I'm guessing the previous owner's pool service was chlorinating the pool with hypo-cal. Anyways, should I go ahead and replace some of the water to get the calcium down below 350? There's no evidence of scaling that I can see, but I feel like the water could be slightly more clear. Will calcium slowly fall with summer evaporation, or is replacing water the only way to lower it?
    1982 built 15K? gallon IG gunite/plaster, DE filter, Pentair Challenger 1.5HP pump, Polaris 280, Pentair LA01N booster pump, 3-8' with diving board, K-2006 test kit

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    Mod Squad jblizzle's Avatar
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    Re: Lower calcium hardness?

    The calcium did come from the tap water. When the pool evaporates, it leaves the CH and you add more when you top it off. It could also be from cal-hypo. Mine has gone up almost 300ppm in the last 2 years just due to evaporation.

    The CH will always rise due to refilling ... unless you get a LOT of rain which could lower the CH.

    Yours is really not that high yet, you should be good for another year or so before you may want to replace water. Just have to keep you pH a little lower.
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
    500 sqft Heliocol solar panels, ThePoolCleaner, TF-100 test kit w/ SpeedStir
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    danimal67's Avatar
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    Mar 2015
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    San Diego, CA
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    Re: Lower calcium hardness?

    Hey JBlizzle,

    Is there a target number for the CH being too high and requires water changing?
    3300 Gallon Vinyl Intex AG Pool. 15'x 3' Round. 2100 GPH Intex Sand Filter/Pump.
    Installed summer of 2014. TF100 Testkit.

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    Mod Squad jblizzle's Avatar
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    Re: Lower calcium hardness?

    The higher it gets, the higher the probability of calcium scaling if you do not maintain tight control of the TA and pH. Over 1000 gets very difficult, but I would not wait that long.
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
    500 sqft Heliocol solar panels, ThePoolCleaner, TF-100 test kit w/ SpeedStir
    Pool School + Test Kit + PoolMath = A TROUBLE FREE POOL
    If you found TFP helpful and we saved you money ... Become a TFP Supporter!

  5. Back To Top    #5

    Join Date
    Jun 2011
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    Re: Lower calcium hardness?

    Ward, if it makes you feel more comfortable, I just brought my CH down from ~1000 to 450. I did two partial drains of my pool and refilled the water with soft water. I'm very happy with 450 and will just make sure that my pH stays low. My pH was ~8.4 when I started and now it's ~7.2 (I don't want it to rise past 7.5 or so).

    I've got quite a bit of calcium stains on the pool (just bought the house late last fall) so it'll take me a while to clean those up, but I don't expect any additional staining at 450. And my CH will rise a bit as the water evaporates and the autofill replaces that water with city water.

    My TA's at ~140 so I'm slowly working on reducing that number. I'd like to get it down to below 100, as that would help my CSI (calcium saturation index). Unfortunately, I'm leaving the cover on right now to warm up the water so the pool's not getting aerated.

    I plan on doing another partial drain/refill this fall or next spring to keep the CH down; refilling with soft water.

    Play around with the pool calculator and see what changing your pH, TA, CH, CYA and temperature does to your CSI.

    Edit: I just checked my TA; it's down to 70 so that gives me a lot more room to let the pH rise without worrying about the CSI.
    Our pool is 15,000 gallons fresh water with a Hayward C5025 cartridge filter system; inground plaster. We bought the house Oct 2014.

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