How much muriatic acid to lower TA?

Mobius5

Member
Jul 6, 2017
17
Buckinghamshire, UK
Hi all,

Currently looking at getting the chemicals I need before pool fill. I tried having a go at this through the calculator but couldn't work it out.

Pool total alkalinity is currently ~ 330 mgHCOl/3 (water board figures, but will have a Lovibond 6-1 tester to confirm for fill)

I will be adding Muriatic Acid (36%) to lower alkalinity and then aerate to raise the pH back. Obviously I will need to do this gradually to ensure pH doesn't go too far out of line, but does anyone know how much MA I will need approximately for a 55m3 pool (14.5K gallon)?

Thanks
 

cowboycasey

Gold Supporter
LifeTime Supporter
TFP Guide
Jul 3, 2013
4,327
Fletcher, OK
You will not know until your done how much it will take... I get a case of 4 gallons and go from there as it will not expire... Keep it away from all your other chemical as it will off-gas some and you do not want it next to chlorine.... :)
 
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setsailsoon

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LifeTime Supporter
TFP Guide
Oct 25, 2015
3,388
Stuart/FL
5,

Amount of acid required depends on the size and chemistry of your pool. You can estimate using Pool Math in the "effects of adding" section. When you are dropping pH to low 7's just drop no more than .4 pH units at a time. For reference, on my pool a little smaller than yours I add about 32 oz of 31.45% at a time. When I drop from 8 to low 7's it takes 2-3 additions of this amount.

Hope this helps.

Chris
 

Stoopalini

Gold Supporter
Jun 8, 2020
419
Central Texas
I just filled a 14k gallon pool last week, and had a TA of 160 to start. I did what you are describing, and added MA when pH got to 7.8-8.0, to bring it down to 7.2. Then aerated to bring the pH back up, and added MA again, repeat.

It took about 1 gallon of 31.45% MA, and 5 days, to get the TA from 160 down to 90. I ran my waterfall about 8 - 10 hours a day during this process.

You will definitely need more MA than it will take to lower the TA though. You'll need to continue adding it to compensate for pH rise as the plaster cures and also as make-up water is added to the pool to keep the water level up.

I bought 1 gallon prior to the fill. When my pool builder came out the day after the fill, he left me 2 additional gallons of 31.45%. Then when the PB's tech came out 3 days later, for the official start-up (which I had already done though), I asked the tech if he could leave me whatever chemicals he would have added if I hadn't already stabilize the water. So he left me 2 more gallons of 31.45%, as well as a pile of trichlor pucks (which I am using right now to bring my CYA up to target).