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Thread: What are the dangers of low CH?

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    Guest

    What are the dangers of low CH?

    I've finally determined that my CH is really low.. Around 150-175.

    Previously, I had trouble getting an accurate test due to metals in the water, but that problem seems to have dissappeared and last night I was able to do an accurate CH test

    My pool is fiberglass and the rest of my numbers look good, except for PH is a little low.
    I've heard that getting the Calcium hardness up a little could help with stain problems - is that true?

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    MikeInTN's Avatar
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    Re: What are the dangers of low CH?

    Copied from Pool School :

    CH - Calcium Hardness

    Calcium hardness indicates the amount of calcium in the water. Over time, water with low calcium levels will tend to dissolve calcium out of plaster, pebble, tile, stone, concrete, and to some extent fiberglass surfaces. You can prevent this from happening by keeping the water saturated with calcium. In a vinyl lined pool there is no need for calcium, though high levels can still cause problems. A plaster pool should have CH levels between 250 and 350 if possible. Calcium helps fiberglass pools resist staining and cobalt spotting. If you have a spa you might want to keep CH at at least 100 to 150 to reduce foaming. CH contributes to the CSI which indicates the tendency for paster damage or calcium scaling.

    You increase CH with calcium chloride, sold as a deicer and by pool stores, or calcium chloride dihydrate, sold by pools stores for increasing calcium. You lower calcium by replacing water.
    24' x 52" AGP - approx 13,500 gallons
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    Re: What are the dangers of low CH?

    Quote Originally Posted by MikeInTN
    You increase CH with calcium chloride, sold as a deicer and by pool stores, or calcium chloride dihydrate, sold by pools stores for increasing calcium. You lower calcium by replacing water.
    Since one chemical seems to always cause another measurement to change . . . do I have to worry about calcium chloride or calclium chloride dihydrate changing any other readings other than the CH? I am only trying to get our CH from 230 to between 250 and 350 as recommended and we finally have most of our measurements pretty close to what they should be - I just don't want to rock the boat.
    Thanks.
    25x15 ft; 11,200 gal; indoor/in ground; plaster (redone 2006); cartridge filter; +40 years old original with the house;
    pool has a cover and we cover the pool half way b/c when it is covered all the way our numbers get screwed up;we don't use the pool very often; only indirect sunlight; Chicago area

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    JasonLion's Avatar
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    Re: What are the dangers of low CH?

    Calcium won't change any of the other levels in any significant way.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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  5. Back To Top    #5
    Guest

    Re: What are the dangers of low CH?

    I should mention that my CH was extremely low when I opened the pool this summer. Under 100ppm.
    I don't believe I was ever checking it properly all of last summer.

    It's been somewhat difficult getting it into my target range of around 250-300.. It's around 230 now and I'm actually chlorinating a bit with Cal-Hypo to help. So far, it does seem to be helping keep the stains at bay.

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