Lowering TA with Dry Acid Or Muriatic Acid

[CelticDaddio]

My TA is currently 230. It was recommended on another forum that I lower it according to the "HOWTO: Step-by-Step Guide to lowering your alkalinity" sticky. I read in my copy of "The Ultimate Guide to Pool Maintenance" by Terry Tamminen that you can lower TA by adding Muriatic Acid, or Dry Acid. Anyone try that?

Ed

[JohnT]

Sure adding acid lowers your TA. It also lowers your pH. When the pH goes back up, the TA goes with it, but when you aerate while the pH is low, the TA stays down.

[CarlD]

Tamminen gives the typical garbage the pool industry gives you. They love the "slug of Muriatic Acid" approach and give you a MacBeth Witches' explanation for why it works. If it does, it's incidental.

There's really only one way, short of dilution with low T/A water to lower T/A and that's what's here. It's not always clear so here's how you do it:

1) Lower pH to 7.0-7.2. (Muriatic or dry acid are both fine) This lowers T/A somewhat.

2) Aerate your water. This raises pH WITHOUT raising T/A--and it's the ONLY WAY TO DO IT!

3) Lower your pH again to 7.0-7.2, bringing T/A down some more.

4) Aerate to raise pH again without raising T/A.

5) Repeat until T/A is in the desired range.

You "ratchet" your T/A down. T/A and pH are linked. pH goes up, T/A goes up. pH goes down, T/A goes down. ONLY BY AERATION can you break that cycle and do the raising of the pH without raising T/A, allowing you to lower it more the next cycle.

The "standard" method only works if you have inadvertent aeration to raise pH that makes it look like it worked.

Worse, the "Slug" of Muriatic Acid can do major, even catastrophic damage to your pool. If that "slug" comes to rest on a vinyl liner, with its 30% concentration of HydroChloric Acid, it can dissolve your liner or weaken it enough to fail.

[CelticDaddio]

How do I aerate the pool?

Ed

Tamminen gives the typical garbage the pool industry gives you. They love the "slug of Muriatic Acid" approach and give you a MacBeth Witches' explanation for why it works. If it does, it's incidental.

There's really only one way, short of dilution with low T/A water to lower T/A and that's what's here. It's not always clear so here's how you do it:

1) Lower pH to 7.0-7.2. (Muriatic or dry acid are both fine) This lowers T/A somewhat.

2) Aerate your water. This raises pH WITHOUT raising T/A--and it's the ONLY WAY TO DO IT!

3) Lower your pH again to 7.0-7.2, bringing T/A down some more.

4) Aerate to raise pH again without raising T/A.

5) Repeat until T/A is in the desired range.

You "ratchet" your T/A down. T/A and pH are linked. pH goes up, T/A goes up. pH goes down, T/A goes down. ONLY BY AERATION can you break that cycle and do the raising of the pH without raising T/A, allowing you to lower it more the next cycle.

The "standard" method only works if you have inadvertent aeration to raise pH that makes it look like it worked.

Worse, the "Slug" of Muriatic Acid can do major, even catastrophic damage to your pool. If that "slug" comes to rest on a vinyl liner, with its 30% concentration of HydroChloric Acid, it can dissolve your liner or weaken it enough to fail.

[JohnT]

How do I aerate the pool?

Ed

A fountain, point the returns at the surface, or get a bunch of kids in there to splash around.

[CelticDaddio]

You mean just a plain ol' fountain like this:



And point the skimmer returns up to the surface?

Ed

A fountain, point the returns at the surface, or get a bunch of kids in there to splash around.

[CarlD]

That's all you need!

[waterbear]

Tamminen gives the typical garbage the pool industry gives you. They love the "slug of Muriatic Acid" approach and give you a MacBeth Witches' explanation for why it works. If it does, it's incidental.

Tamminen doesn't actually advocate the 'slug method' in his book. He just gives some treatment tables that show how much muriactic acid or dry acid is needed to lower a certain amount of TA in a given volume of water and doesn't really say much more on the subject. All references he makes about adding acid always say to add it in small amounts so as not to make too great a pH change at once and to 'walk' the acid around the pool or pour it slowly into the return stream with the pump running so it gets diluted quickly and to never pour it near drains, skimmers,and other suction inlets. Basically the same advice that has been given on this board time and again. His advice might not be complete (his whole chapter on water chemistrt is VERY basic) but it is generally sound.

[peggles0224]

I have borderline Alk reading of 70 and 7.9 PH... How much baking soda do I had to raise Alk and how much Muriatic acid do I had to lower PH

[CarlD]

I have borderline Alk reading of 70 and 7.9 PH... How much baking soda do I had to raise Alk and how much Muriatic acid do I had to lower PH

Say you have a 15,000 gallon pool. Start with 1 lb of baking soda and 1 cup of muriatic acid. I'd add them at least an hour apart (acid first), then wait a few hours (say 6?) and measure pH and T/A again. Go slow, use a little bit at a time so you don't overshoot targets. If you lower pH from 7.9 to 7.3, T/A should come down still further.