2 Gallons of Muriatic Acid???

Problems relating to pH and total alkalinity.
Increase ph, increase TA. Reduce pH, reduce TA.
pH chemistry advice and techniques for the pool.
Guest

2 Gallons of Muriatic Acid???

Postby Guest » Sat 23 Jun, 2007 20:25

My alkalinity is at 188ppm I was using the calculators to calculate how much muriatic acid to use and to with a 14,000gal pool to drop the alkalinity 90ppm it said to use 2gallons. Is that right?


Buggsw
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Postby Buggsw » Sat 23 Jun, 2007 20:58

Which calculators were you using?

I don't have any handy that show the amount to lower Alk. Mine only show how much to lower pH and I think that is as a precaution so people don't just throw a bunch of acid in their water and causing the pH to go way low.

pH is the number you really want to keep an eye on. You don't want to lower your pH too low or you can start to see some heavy corrosion.

Therefore, to lower your Alk you start with a higher pH and lower your pH to 7.0, however much your Alk lowers is what you get. Then you aerate your water until your pH rises back up to 7.8 or so and lower your pH again with the proper amount of acid to lower it to 7.0 and repeat the process as often as it takes to get your Alk down.

There are many posts that explain the procedure - look for posts with answers by Chem Geek.
Guest

Postby Guest » Sat 23 Jun, 2007 23:05

Buggsw wrote:Which calculators were you using?

I don't have any handy that show the amount to lower Alk. Mine only show how much to lower pH and I think that is as a precaution so people don't just throw a bunch of acid in their water and causing the pH to go way low.

pH is the number you really want to keep an eye on. You don't want to lower your pH too low or you can start to see some heavy corrosion.

Therefore, to lower your Alk you start with a higher pH and lower your pH to 7.0, however much your Alk lowers is what you get. Then you aerate your water until your pH rises back up to 7.8 or so and lower your pH again with the proper amount of acid to lower it to 7.0 and repeat the process as often as it takes to get your Alk down.

There are many posts that explain the procedure - look for posts with answers by Chem Geek.


Awesome, thank you for that informative response. That makes perfect sense.

Also what is the best way to aerate the water? By using a garden hose and just spraying the surface?
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Postby chem geek » Sun 24 Jun, 2007 00:08

My spreadsheet will calculate how much acid it takes to lower TA, given a starting and ending TA and starting/ending pH. With a pH of 7.5 and TA going from 188 to 90 (and assuming a CYA of 30 ppm), it would take 44 cups (2.75 gallons) of Muriatic Acid in total, but obviously that is not added all at once. Just to get the pH down from 7.5 to 7.2 takes 4.7 cups (or 9.3 cups to go from 7.5 to 7.0), but then lots of aeration is needed and lots more acid addition in small increments to keep the pH down.

This post describes the procedure and it goes faster if you keep the pH low rather than let it go all the way up to 7.6. Outgassing is faster at lower pH.
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Postby Backglass » Sun 24 Jun, 2007 19:37

Anonymous wrote:Also what is the best way to aerate the water? By using a garden hose and just spraying the surface?


The best way is with a waterfall or fountain...but some of us (like me) dont have such luxuries! ;)

I just turn my return eyeball straight up and it gurgles enough to raise the ph...albeit slowly. A garden hose wont help unless you are actually pumping pool water from your pump through it.
Lwelch

TA vs. pH

Postby Lwelch » Mon 25 Jun, 2007 20:55

My TA reads approx 220 ppm. pH reads approx 7.3. I tried lowering the TA with a protracted addition of Mur. Acid .... got it down to 120 ppm. I then added Sodium Carb to raise the pH back to 7.3 .... no problem other than the TA went right back to 220. Am I missing something here ?[/b]
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Postby chem geek » Tue 26 Jun, 2007 00:28

Lwelch,

Acid lowers both pH AND TA while base raises both pH AND TA so you just yo-yo back and forth. In your case, it's even worse, because the base you used, sodium carbonate found in pH Up products, is not only a base, but also raises alkalinity. It is identical to adding lye (a pure base, sodium hydroxide) AND Alkalinity Up (sodium bicarbonate).

See this link for the procedure to lower TA and notice that the most critical and important element of it is aeration at low pH. Notice that there is NO addition of a base in the procedure. To raise the pH at the end, you just aerate.

Richard
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Postby Guest » Tue 26 Jun, 2007 20:39

Backglass wrote:
Anonymous wrote:Also what is the best way to aerate the water? By using a garden hose and just spraying the surface?


The best way is with a waterfall or fountain...but some of us (like me) dont have such luxuries! ;)

I just turn my return eyeball straight up and it gurgles enough to raise the ph...albeit slowly. A garden hose wont help unless you are actually pumping pool water from your pump through it.


Ahh ok cool thanks for clearing that up

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