
Originally Posted by
PoolDoc
One of the reasons I'm not in love with the pool calculator is that it tends to encourage people toward a 'fix it in one dose' approach to chemistry. This was a BAD idea, when pool stores pioneered that approach, and it's a BAD idea now.
There IS an exception: low chlorine should be fixed in one dose, and usually, more is better. (More as in 3x too much, not 50x too much!)
For everything else, it's much, much better --- in PRACTICE --- to dose, test, and re-dose if needed. For your 25-30,000 gallon pool, you are around 1/5 of a million pounds of water. So, if you add 1 lb of CYA, your CYA level will increase by 4 - 5 ppm. Calcium chloride dihydrate ends up being about 60% 'active' with respect to CH test results, so 1 # of Calc chloride will add 2 - 3 ppm calcium hardness.
So, if you wanted to increase your CH by 60 ppm, you'd need to add 20+ lbs of calcium chloride. But DO NOT DO THIS! As mentioned above, it's a generally bad idea. But, in a pool with a chemistry approaching calcium carbonate saturation, ANY large addition of pH+, alkalinity+ or calcium+ will tend to precipitate a cloud of calcium carbonate.
What's the solution? If you need to take a pool to saturation -- and you probably don't -- SMALL repeated doses are a much, MUCH better way to do it. So, instead of adding 20+ lbs, add 5 -10 lbs and then retest.
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