Quote Originally Posted by chem geek View Post
[The accurate calculation is complicated and is done in my Pool Equations spreadsheet. I didn't provide a simple enough formula to be used online in a timely manner.
Of course, even if the problems with the PoolCalculator *were* fixed, that would do nothing to resolve the issues with testing errors.

Like I said before, if you need to know how much acid or base to add, all at once, MEASURE it; don't calculate it. But, I strongly, strongly recommend against an all-in-one dose. If if you measure it perfectly, and even if you measure your doses perfectly, there's a 30% chance that your pool volume figure is off by 30% or more.

So -- at MOST -- add 1/2 of the dose calculated from an acid / base test, and then RE-TEST.

I have enormous respect for Richard's chemical knowledge and analytical acumen, but this is an area where we disagree rather dramatically. His approach, embedded in the PoolCalculator, is the SAME one followed by pool stores, and suffers some of the same problem: high precision calculation, based on LOW precision testing and pool volume data, used to determine ALL-AT-ONCE doses.

It's a bad idea in pool stores, and it's not a better one, simply because Richard's analytical formula are somewhat more accurate than the BioLab Alex program.

It works for Richard, both in theory and in practice, because he is preternaturally precise. I'm guessing he hasn't made a math error in 10 years! If you are the same . . . his approach may work for you.

But, for the other 99.99% of the world, trying to single shot pool chemical doses is a fast train to pool problems.

The ONLY times you should single-shot a large dose, is when you're adding chlorine under conditions (like heavy algae) where "too much" is almost certainly "not enough", or when you are adding something, like polyquat, where "too much" won't hurt anything but your wallet. All the rest of the time, you should NEVER add a complete single dose. Not with acid; not with bases; not with calcium; not alkalinity (baking soda).

If you have low calcium in your pool, and low carbonate alkalinity, AND you want to single shot your borax dosing (for 50 - 60 ppm borates) AND you have plenty of muriatic acid on hand, AND plenty of time, to stay with it till you get the pH back down -- if ALL those things are true, then if you want to, I suppose a single shot dose of borax to 60 ppm borates might be OK. I don't recommend it, but it will probably work out OK.

All the rest of the time, for your sake, and the sake of your pool, please leave the ALL-AT-ONCE dosing to Richard, and that tiny fraction of the human population who is as meticulous as he is.