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Thread: cal-hypo to raise CH

  1. Back To Top    #1

    Join Date
    Oct 2010
    Location
    Houston, TX
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    152

    cal-hypo to raise CH

    Hi, my calcium hardness level appears to be low for my plaster pool, but CSI seems to be ok.

    Numbers:
    pH 7.8
    TA 130
    CH 140
    CYA 70
    temp 60 deg

    CSI turns out to be -0.05. I have a 4500 gallon spa with a plaster surface.

    Some questions:

    1) Is it essential to raise CH levels if my CSI appears ok?
    2) lf I wanted to raise CH, can I just use cal-hypo tabs to do this which will reduce the amount of bleach I have to add as well?
    3) How long will it take for the cal-hypo tabs before CH level is appropriate?
    4) Also, I've read dissolving cal-hypo in a bucket then pouring it in, but can I instead use one of those pool floaters and just place some tabs in there to distribute the cal-hypo slowly?

    Thanks!
    15k gunite pool. Intelliflo VF. Autopilot SWG.
    2k separate spa with waterfall (ie: pain in the rear maintaining a separate body of water). 2HP Hayward Tristar pump.

  2. Back To Top    #2
    Guest

    Re: cal-hypo to raise CH

    Calcium is critical to plaster, and you should be between 200-400 ppm calcium. I don't see a calcium reading in your specs, but I assume you know what it is.

    Why not just get some calcium chloride if you need to raise the CH? It is cheap and you don't have to add all that other stuff or guess how much you need.

  3. Back To Top    #3

    Join Date
    Mar 2007
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    San Rafael, CA USA
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    Re: cal-hypo to raise CH

    You do not need to raise your CH level. It is calcium carbonate saturation (which is what the CSI calculates) that is important for plaster, not calcium alone at any particular level. Not only is the CSI what is important, but even then you only need to be in the ballpark with it. Your higher pH and TA levels are currently compensating for the lower CH. So long as your pH isn't rising too quickly from the higher TA, then what you've got is fine. If at your next water drain/refill (for a spa) or in the summer you end up lowering your TA substantially and target a lower pH, then you could consider increasing the pH, but I wouldn't worry about this now.

    Yes you could just use Cal-Hypo as your source of chlorine in order to raise the CH level in the future if you need/want to do that. For every 10 ppm Free Chlorine (FC) added by Cal-Hypo, it will increase your CH by around 7 ppm so you can figure how long it will take based on your chlorine usage.

    Cal-Hypo tends to dissolve too quickly and needs a special type of chlorinator for that purpose. You most certainly do not want to put it into a standard floating chlorinator or inline chlorinator that has had Trichlor in it, ever, because the two can cause an explosion or fire (see this link for a video).
    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
    Oct 2010
    Location
    Houston, TX
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    152

    Re: cal-hypo to raise CH

    Thanks for the tips. That video of the cal-hypo and trichlor explosion is crazy! I can see a lot of novices such as myself making this mistake considering they are both chlorine sources...

    what's the best way to add cal-hypo to a 4500 gallon spa like mine by the way?
    15k gunite pool. Intelliflo VF. Autopilot SWG.
    2k separate spa with waterfall (ie: pain in the rear maintaining a separate body of water). 2HP Hayward Tristar pump.

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    guamguy's Avatar
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    Feb 2010
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    Guam, USA
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    Re: cal-hypo to raise CH

    I usually pre-dissolve the amount I want to add in a bucket of water, then slowly pour in over a return
    12,800 gallon IG plaster kidney-shaped pool, waterslide, 800 gallon spa.
    1HP 2 speed Sta-Rite pool pump, 1.5 HP Sta-Rite spa jet pump. 2 skimmers, 1 main drain
    Purex-Triton TR-60 325 lb.sand filter. 2" Plumbing, Intex SWCG, TF-100 test kit.
    Link to pics of my pool! http://www.troublefreepool.com/my-oasis-t26558.html

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    JasonLion's Avatar
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    May 2007
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    Silver Spring, MD
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    Re: cal-hypo to raise CH

    Keep in mind that cal-hypo gets really hot while it is dissolving. If you dissolve too much at once you can get burned, or melt the bucket. This isn't normally a problem, just something to be aware of.
    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

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