Muriatic Acid

Jlady121

Active member
Apr 7, 2017
26
Channahon, IL
PH is 8.1 and want to drop it. Pool math said add 33 Oz of muriatic acid for my 22k gallon pool. Pool store was saying 83 oz. I don’t usually listen to anything they recommend but wanted to make sure I was not calculating wrong.
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
34,632
Laughlin, NV
Need more data. What is your TA? That effects how much acid is needed.

You cannot test a pH of 8.1 with the color match kit.
 

Jlady121

Active member
Apr 7, 2017
26
Channahon, IL
No idea. Without accurate testing data we do not know. Pool store tests are not used for guidance here on TFP.
I understand it’s not ideal, and in a perfect world I would only use the test kit. I just wanted to know if I was missing a step when calculating the result with the recommended dosing.
 

Jlady121

Active member
Apr 7, 2017
26
Channahon, IL
Maybe I'm over-simplifying, but pool math says 33oz and pool store says a lot more than that. Simply add the 33 oz and re-test in 30 minutes to see if you hit the pH you were looking for. If not, repeat until you get there.
Thank you! I may have been overthinking it all. Usually the pool store recommendations are crazy, but wanted to make sure I’m not using the calculator wrong when entering results.
 

Rattus Suffocatus

Silver Supporter
Jun 5, 2019
1,290
Corona de Tucson, AZ
Exactly, put in the 33 oz... wait an hour... test pH again. If you have no test kit at all that same Ace (and Home Depot, same kit under two different names) sells one for about $15 that will at least do pH and TA properly (OTO chlorine too, though FAS-DPD is much more accurate)... You do want the Taylor/TFP kit for everything else because you do need the other values such as CH to accurately determine the CSI (Saturation Index) of the pool so you know where to set your pH in the first place. But I use a kit like that as a secondary verification to the Taylor/TFP kit... and it's within range every time.

It will at least get you to get your pH set in the meantime, though not 100% balanced without the CH reading.

83 oz is more than a half a gallon. Now in a 21k pool if that Muriatic acid is 14% then I could actually see that with the pH being that high. If it's normal 29% (pool store)-31.5% (normal hardware store grade 20 degree Baume) that seems high -- enough that even if it were correct I'd do half and half anyway... that's a lot of acid.

In the Chicago suburbs (I grew up in Elk Grove), depending if your fill water is all well or has some Lake Michigan added in, I'd guess that the 83 oz is high. Do the half and half and then you'll be safe. 33 oz is probably quite reasonable for a pool that size with normal MA and will not be enough if it's the 14% stuff.