How much Muriatic Acid?

I am compiling a sheet for the cover of my new BBB Pool book to help cut down on confusion while I'm still getting the hang of this concept. I've found instructions for how much bleach, borax and baking soda to add, but I haven't found any instructions for how much Muriatic Acid to add if you need to lower your pH. Can someone tell me the formula for that, please? Thanks

Get the BleachCalc and use it to determine your acid dosing.

How does the bleach calculator help with acid dosing?

I can at least speak to what I do. If my pH reading has shot up to the first high reading, which I believe is 7.8, in my 20,000 gallon pool, a full cup will bring it down into range. If you're unsure, modify according to the size of your pool and cut the amount in half, then retest a few hours later or the next day and see if you're good or need to add a bit more. You will soon learn how much your pool requires to bring it back into range.

Be sure to wear gloves and eye protection, or close your eyes as you're pouring it in in front of your deep end jet. And, hold your breath until you've got the acid jug recapped. And if you can, keep holding your breath while you quickly walk away from the area as the fumes are still in the air; more than just obnoxious, they're dangerous!

Elsie - BleachCalc can do pH calculations in addition to a host of others via its "More Calcs" menu. Just enter your pool size and it gives you an estimate of how much Muriatic acid to add to lower (or Sodium Carbonate to add to increase) your pH by 0.2.

I think bleachCalc (PH menu) uses the following formula:

Pool Volume (gallons) * .0008 = oz of acid for .2 PH down.

Another rule of thumb is that you should not put in more than a pint per 10000 gallons at one time.

The actual amount of Muriatic Acid you need to add to get a desired change in pH is dependent on the starting and ending pH as well as the TA level. The formula given in the previous post works correctly going from 7.7 to 7.5 with a TA of 110. Therefore, the advice of adding less than the calculated amount and seeing the effect before adding more is good.

If I can figure out how to simplify the formulas that account for starting/ending pH and current TA, I'll update Michael Smith (the creator of BleachCalc) with some new formulas that will be more general. I have a spreadsheet that calculates all this stuff, but it is way too complicated for general use (though I'm working on simplifying it).

Richard

Thanks everyone!