Chlorine Bleach & pH

[PoolDoc]

Ignore that dumb book*. It's wrong! That nutty thing was one of the reasons I started making my own kits (and still would be, if I was a better business man).

I ran a 300,000 gallon public pool with hundreds of swimmers, on straight industrial 15% bleach for THREE years, and never used a single bit of acid!

-- You can use the ABD tables, if you like --

*There is a reason why the book says what it does, and there's a reason why it's wrong in practice but the explanation runs to very long.

[SnoopysGirl]

Okay, so what you are both essentially saying is that my fill water is likely the problem, & probably the reason I wasn't having pH and TA issues BEFORE switching to liquid chlorine is because of the acidity of the trichlor tabs I was using? Ben, the ABD tables - are those the ones in the Taylor book? Sorry, I am not familiar with ABD tables. Let me know if there is a link I am missing.

[PoolDoc]

ABD => Acid / Base Demand.

Using trichlor with high alkalinity fill water would tend to compensate for the pH issues with the water. Bleach, used routinely, has almost no impact on pH or TA. When you FIRST add a dose, it does raise both somewhat.

[SnoopysGirl]

I tested our fill water today. pH is 7.2 TA is 390. pH is rising, though, is that due to the high alkalinity? This is confusing me. Should I at some point add muriatic acid?

[PoolDoc]

fill TA is 390. . . . .Should I at some point add muriatic acid?

Uh, wow. You'll be adding muriatic acid at some points, and some other points, and still some other points after that, with adding TA=390 water. With a 30K gallon pool, and that TA, you probably need to think in terms of 1/2 gallon doses, every time your pH exceeds 7.2, at least till your pool's TA is below 120 ppm. Just make it part of your routine.

But . . . read the muriatic acid guide linked in my signature.

[waterbear]

pH is rising, though, is that due to the high alkalinity?

Yep. the higher the TA the faster pH rises (because of faster outgassing of carbon dioxide)
The lower you put the pH the faster the pH rises (because of faster outgassing of carbon dioxide)
The more you aerate (move) the water (by water features, spillovers, fountains, splashing kids, negative edged, SWCGs, etc.) the faster the pH rises (because of faster outgassing of carbon dioxide)

[SnoopysGirl]

Yep. the higher the TA the faster pH rises (because of faster outgassing of carbon dioxide)
The lower you put the pH the faster the pH rises (because of faster outgassing of carbon dioxide)
The more you aerate (move) the water (by water features, spillovers, fountains, splashing kids, negative edged, SWCGs, etc.) the faster the pH rises (because of faster outgassing of carbon dioxide)

Thank you for the replies! I am looking at the tips page, and how to effectively lower alkalinity, and it specifies aerating to LOWER the alkalinity. Do I aerate to lower or will that increase alkalinity?

Also, I have some leftover sodium bisulfate. Can I use that to lower pH/alkalinity? It would save me some $$, and it would use up product that was already here.

[PoolDoc]

To lower your alkalinity, you need to lower your pH to near 7.0, and aerate.

Got ahead and use your sodium bisulfate for that.

Also -- we're trying to get the Pool Chart data entered into user's signatures -- please check yours and see if it's correct.

[SnoopysGirl]

Great, I will use what I have and then switch to the muriatic acid per instructions listed in your sig.

My stats have changed a bit since joining: now using liquid chlorine 10%, Taylor K2006 test kit (smaller bottles - don't know which kit that is). Also, I don't see my heater listed. I have a Jandy Lite 2 pool heater.