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Thread: Fill water has low CH, but pool water is high CH?

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    Fill water has low CH, but pool water is high CH?

    Using my TF-100 kit w/ speedstir, today I tested not only the pool, but also the water coming out of the well I use to fill/replenish, and here are the results:

    Well
    FC = 0
    CYA = 0
    pH = 7.2
    TA = 440-450
    CH = 350

    Pool
    FC = 11.5
    CC = 0
    CYA = 60
    pH = 7.2
    TA = 120
    CH = 525

    No real surprises there for me, except the CH - why/how is the water going from a CH of 350 to 525, and should I care? It's a plaster pool built in '85, never been painted or re-plastered, and has no cracks, only surface etching from where MA was previously added in slugs (according to local pool store)
    In-ground Plaster 40' X 80' 144K gallon pool w/ 2 pumps (old Challenger bronze and newer Challenger II plastic) and 2 large sand filters (Pentair Triton 140's). Built in '85, in bee-yootiful shady Buffalo Gap, West Texas.

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    jjslinger's Avatar
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    Re: Fill water has low CH, but pool water is high CH?

    Someone who knows more than me will surely reply soon, but here is one explanation. As water evaporates, the calcium stays in the pool; then more fill water comes in with more calcium. Then more water evaporates. Etc. Eventually, the CH drifts up.

    Don
    16K gal IG 16'x28' pebble since 2011; Pentair Easytouch; Sta-Rite Intellipro VS pump; Sta-Rite 400 sq. ft. cartridge (System 3); 6 Heliocol Solar Panels; Aquamatic Cover; Legend pressure-side cleaner with Hayward booster pump; TF100 Test Kit.

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    Re: Fill water has low CH, but pool water is high CH?

    Quote Originally Posted by jjslinger
    Someone who knows more than me will surely reply soon, but here is one explanation. As water evaporates, the calcium stays in the pool; then more fill water comes in with more calcium. Then more water evaporates. Etc. Eventually, the CH drifts up.

    Don
    That may well be the case, since this pool hasn't been drained since Aug '07 (now why didn't I think of that???)

    Anybody see a reason to be concerned? CSI as per the pool calculator is -0.01, the target? is -0.22.
    In-ground Plaster 40' X 80' 144K gallon pool w/ 2 pumps (old Challenger bronze and newer Challenger II plastic) and 2 large sand filters (Pentair Triton 140's). Built in '85, in bee-yootiful shady Buffalo Gap, West Texas.

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    jjslinger's Avatar
    Join Date
    Sep 2011
    Location
    Santa Rosa, CA
    Posts
    97

    Re: Fill water has low CH, but pool water is high CH?

    Quote Originally Posted by jamyers
    That may well be the case, since this pool hasn't been drained since Aug '07 (now why didn't I think of that???)

    Anybody see a reason to be concerned? CSI as per the pool calculator is -0.01, the target? is -0.22.
    More knowledgeable people will respond, but I think the CSI target is 0; +/-0.3 is considered "okay"; beyond that, the pool calculator may start giving some warning comments. I like to keep my CSI as close to 0 as possible.

    Don
    16K gal IG 16'x28' pebble since 2011; Pentair Easytouch; Sta-Rite Intellipro VS pump; Sta-Rite 400 sq. ft. cartridge (System 3); 6 Heliocol Solar Panels; Aquamatic Cover; Legend pressure-side cleaner with Hayward booster pump; TF100 Test Kit.

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