Muriatic acid 20%

[elaineinspain]

I’m in Spain and the only Muriatic acid I can buy here is 20%

Up till now I’ve been estimating how much to add, basing my guess on the “effects of adding Muriatic acid 31.45%” in the drop down menu on the app, and I’ve had reasonable results as I’ve only been adding it a litre or so at a time to reduce the pH.
However I want to add borax to my pool water. I’ve been reading up on it and understand about adding MA to balance out the pH and the TA.
My problem is I’m not so good at math and because I’ll be adding a lot of MA I was hoping there might be some math geniuses here who can help me work out a formula to convert 31.45% to 20%

Up till now I’ve been looking at the 31.45% figures and calculating that 20% is roughly 2/3 of 31.45 %
So when I add 2 liters of acid the change will be a reduction of 0.6pH, instead of 0.9,and this is in the ball park of what I’m actually producing, usually my results are a little less ~ a reduction of 0.5

Is there anyone here who can help me work it out more exactly?
Thank you

 

[KenKasza]

Just my opinion, but your math is close enough. Rough is OK. 0.6 drop or 0.5 drop, how do you tell the difference? No need to be that exact.
The difference you are seeing can be attributed to how you are measuring your chemicals. Or your pool is a bit larger the 70000.
When you add other chemicals, are those results always a bit lower than expected? If yes, then increase your pool size to 72000. That will make up the difference.

 

[DrewLG]

Up till now I’ve been looking at the 31.45% figures and calculating that 20% is roughly 2/3 of 31.45 %
....
Is there anyone here who can help me work it out more exactly?

To convert from volume of 31.45% to volume of 20%, multiply by 1.5725. So if PoolMath says to add 14 liters of 31.45%, you should add 14 x 1.5725 = 22 liters of 20%.

Your 2/3 estimate is within 5% of the exact ratio: Using your estimate, you would add 14 x 1.5 = 21 liters.

But remember that unlike most of the other calculations in PoolMath, the pH calculations are only rough estimates. So if you wanted to be cautious, it would make sense to add a little less than the suggested volume -- for example, adding 1.5x as you have been doing, rather than the exact 1.5725x. Then test and add more if necessary.

 

[elaineinspain]

To convert from volume of 31.45% to volume of 20%, multiply by 1.5725. So if PoolMath says to add 14 liters of 31.45%, you should add 14 x 1.5725 = 22 liters of 20%.

Your 2/3 estimate is within 5% of the exact ratio: Using your estimate, you would add 14 x 1.5 = 21 liters.

But remember that unlike most of the other calculations in PoolMath, the pH calculations are only rough estimates. So if you wanted to be cautious, it would make sense to add a little less than the suggested volume -- for example, adding 1.5x as you have been doing, rather than the exact 1.5725x. Then test and add more if necessary.

Thanks so much for giving me the formula to work it out.
I’m really pleased that my original 2/3 theory was so close to being correct. I’m not such a dum blond after all!