Muriatic Acid Amount to Add

[jeremye416]

The pool math app shows I should add 5.7 oz of 20 baume muriatic acid to lower the pH from 8 to 7.6.

The Taylor Test kit book says I should should add 14 oz.

The pool is 7500 gallons and the TA is 70.

That recommendation seems low (5.7 oz). Any ideas?

I’m brand new to pool testing and the app.

 

[mknauss]

Welcome to the forum!
That is the amount I get too.
I suggest you read through Pool Care Basics - Trouble Free Pool and even look at a few of our videos TFP-TV - Trouble Free Pool

 

[jeremye416]

Welcome to the forum!
That is the amount I get too.
I suggest you read through Pool Care Basics - Trouble Free Pool and even look at a few of our videos TFP-TV - Trouble Free Pool

I’ve read the articles but can’t find the calculation explained. Can you point me to the muriatic acid calculation article?

 

[mknauss]

There is no calculation 'article'.

You can peruse Pool Water Chemistry

 

[mgtfp]

5.7oz sounds about right for your pool size. Add that and see where it gets you. You can always add more, but un-adding is difficult.

Which advice from the Taylor booklet are you referring to? Have you done an acid demand test?

The required acid amount calculation in PoolMath is based on solving the chemical equilibrium equations involved. These calculations have been done with a more complex tool and the results than basically tabularised for PoolMath. pH calculations are quite complex, there are no simple explanations that I know of.

 

[mgtfp]

If you have done the acid demand test and the Taylor table tells you to add much more than the PoolMath calculation tells you, then the pH is likely higher than 8.0, but you read it as 8.0 because that's where the Taylor comparator ends.

The acid demand test doesn't really care what the starting pH is, you just add drops until you reach the target pH.

But entering 8.0 into PoolMath when the pH is actually higher will of course give a wrong acid amount.

Nevertheless, we don't advise to lower pH by more than 0.4 in one go. Instead go iteratively to avoid overshooting.

If pH is above the max of the comparator (for example 8.0), then assume it to be the max value to calculate the required acid amount. Then retest after running the pump for 30 min and add more if required.