How much Muriatic Acid can I safely add....

Jul 1, 2007
NW Minnesota
was wondering how much muriatic acid I can add to my pool at one time and on a daily basis.

I have High alk (280) and I am trying to get it to come down. PH is 7.4. How much would the daily amount be and how much can I add at one time? What is the best way to add it? Pump running or pump off? My pool is about 3900-4000 gals.


The Mermaid Queen

TFP Expert
LifeTime Supporter
Mar 28, 2007
Northern KY
can't answer how much at once, but use Jason's calculator in my sig to find out how much you need.

You will add it to water (always add acid to water, never the other way) and slowly pour it in front of a return with the pump running.


TFP Expert
Platinum Supporter
LifeTime Supporter
May 7, 2007
Silver Spring, MD
You always want the pump running when you are adding chemicals and for at least half an hour afterwards to help them mix in.

The amount of acid you need to add varies depending on your current PH and TA. Just at the moment you could add two cups of 31.45% muriatic acid, but the amount you can add will go down signifcantly as your TA comes down and at the same time could be higher if you start from a higher starting PH.

The best approach is to add less than you think you need, wait half an hour to let it mix in, retest to see where that got you and repeat as needed.


Mod Squad
TFP Expert
Platinum Supporter
LifeTime Supporter
In The Industry
Apr 1, 2007
Sebring, Florida

If your goal is to lower Alk, that will require aeration in addition to the acid. Before we get into that, just confirm that you are aware that adding acid alone will not lower your Alk.
a good rule of thumb is to add about a pint per 10000 gallons, wait 30 minutes and repeat until your pH is at target. (If you are lowering TA then shoot for a pH of 7.0 and then test the TA and start aerating the water, this will cause the pH to rise. As the pH starts to rise continue adding acid and keep the pH at 7.0 and retest the TA and keep aerating. When the TA is on target stop adding acid and continue to aerate until the pH rises to 7.6. You are now done.)