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Thread: The calcium hand-waving game

  1. Back To Top    #1

    Join Date
    Jun 2012
    Location
    Pittsburgh, PA
    Posts
    7

    The calcium hand-waving game

    I'm wondering if I can get some debunking help.

    Our water-testing system here typically calls for the addition of outrageous amounts of calcium to pools when given a strip water sample. It's a glorified scanner with a color-picker in it where different shades on the strips correspond to ppm's.
    Being that 99.9% of our customers have vinyl liners (that's what we install), I never recommend the addition of calcium. Why buy stuff you don't need, and then have to drain water because the system told you to add 19 pounds of calcium?
    However, I was told that "The amount of calcium in the water determines how much chemicals the pool can hold successfully."

    Total BS? I'm not sure how calcium could affect the capacity of water to hold chemicals. Smells like an attempt to sell unnecessary chemicals to me.

  2. Back To Top    #2
    JasonLion's Avatar
    Join Date
    May 2007
    Location
    Silver Spring, MD
    Posts
    37,879

    Re: The calcium hand-waving game

    The only known differences between very low CH and "normal" CH in a vinyl liner pool is that very low calcium makes foaming slightly more likely and normal/high CH makes metal stains slightly more likely. The foaming effect is very small and almost never matters except in a spa. The metal staining effect involves interactions with sequestrant, which will bind to calcium, reducing the sequestrant available to bind to metals. Calcium levels have no impact on FC, CC, PH, TA, Borate, Salt, or CYA. There is also the non-chemistry issue that low CH can sometimes invalidate heater warranties, not that it makes any actual difference to the heater. And finally, low CH can reduce pool store revenue.

    As always, high CH can be a problem for any pool.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

  3. Back To Top    #3

    Join Date
    Mar 2007
    Location
    San Rafael, CA USA
    Posts
    12,082

    Re: The calcium hand-waving game

    Is your strip-reading test system actually measuring Calcium Hardness anyway? It's probably measuring Total Hardness since most test strips don't test Calcium Hardness.
    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
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

  4. Back To Top    #4

    Join Date
    Jun 2012
    Location
    Pittsburgh, PA
    Posts
    7

    Re: The calcium hand-waving game

    Yes, actually it is total hardness. The scanner, though, just says that pad is calcium hardness. That's an issue.

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