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Thread: confused about calcium hardness

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    Join Date
    Jul 2016
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    palm coast/florida
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    confused about calcium hardness

    We have a salt water pool and I am getting very confused about the calcium hardness. We are finding calcium granules in our filter and some flakes that shoot out the returns. The pool store tested them and said they were calcium. The pool store told us to add acid to lower our ph which was 8.0 at testing. They also told us to add metal binder to lower the calcium levels which were 320ppm. According to your chemistry/pool chemical info you state that a swp should have calcium hardness levels higher than this. I understand that our acid levels need to be stabilized but it sound like we need to be adding calcium not trying to bind it up. Are we causing damage to our pool walls? Help!!

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    Texas Splash's Avatar
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    Re: confused about calcium hardness

    Hello and welcome to TFP! If the particles you are finding are indeed calcium deposits, then your CSI level would appear to be elevated. The potential for calcium build-up/scale increases when the CSI level is over 0.6. You can see this on the Poolmath Calculator (link below) when you load all of your current readings. Of course to do this you must use one of the TFP recommended test kits - either a TF-100 or Taylor K-2006C. Testing at home you will typically see more accurate test results than at the pool store. There is no need to invest in any chemical binding products. My correctly managing pH, TA, and CH, you can achieve a healthy CSI level for your plaster pool.

    If you could post a full set of test results, it might give us a better glimpse of your water condition at the moment.
    Pat (a.k.a. Texas Splash) ~ My Pool: Viking Fiberglass; 17,888 Gal; Waterway Supreme 2-sp/2-hp pump; Hayward Ctg filter; TF-100 w/ Speed Stir
    Vital Links: POOL SCHOOL, RECOMMENDED LEVELS, RECOMMENDED CHEMICALS, Poolmath Calculator, SLAM, Chlorine/CYA CHART.
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  3. Back To Top    #3

    Join Date
    Jul 2016
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    palm coast/florida
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    Re: confused about calcium hardness

    total Chlorine 5.0
    free chlorine 5.0
    ph 8.0
    acid demand 5
    total alkalinity 140ppm
    calcium hardness 320ppm
    stabilizer 40ppm (I haven't added more of this yet)
    total dissolved solids 4,000ppm
    salt 3,400ppm

    this is an exposed aggregate pool with approximately 29947 gallons

    Thank you for your help

    - - - Updated - - -

    Also the pool looks great. No cloudiness etc. and the water temp is about 87 degrees

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    Texas Splash's Avatar
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    Re: confused about calcium hardness

    A couple things about those test results then you can go from there:
    - If these are pool store tests, be very weary of them. Most often they are way off. But let's assume they are yours from a TF-100 or Taylor K-2006C and are accurate ...
    - pH is high; should be 7.5-7.8. The high pH (and elevated TA) raises your CSI level to 0.56 (just under that threshold I noted earlier; potential for scale.
    - Your best bet right now would be to lower pH to about 7.6 and lower TA via the acid/aeration method to about 80; follow the Pool School - Lower Total Alkalinity page.
    - Since you appear to have a SWG pool, your CYA is too low (you commented on that). TFP recommends a minimum CYA of 70. So I would increase that ASAP to help preserve your FC production.

    Hope that helps.
    Pat (a.k.a. Texas Splash) ~ My Pool: Viking Fiberglass; 17,888 Gal; Waterway Supreme 2-sp/2-hp pump; Hayward Ctg filter; TF-100 w/ Speed Stir
    Vital Links: POOL SCHOOL, RECOMMENDED LEVELS, RECOMMENDED CHEMICALS, Poolmath Calculator, SLAM, Chlorine/CYA CHART.
    If you enjoyed your TFP experience, please consider donating to Support TFP!

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    palm coast/florida
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    Re: confused about calcium hardness

    Thank you. I will find out what test kit they use at our pool store and will go add stabilizer now. I added acid this morning, so hopefully the ph has resolved somewhat. I will test it again tomorrow

  6. Back To Top    #6
    Mod Squad jblizzle's Avatar
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    Re: confused about calcium hardness

    Welcome to TFP!!!

    It does not matter what test kit the pool store is using ... there is very often operator error.

    Invest in one of the Recommended Test Kits and take control of your pool.

    Please add your pool details to your signature as described HERE as it will help us help you.
    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
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