High Ph yet Low Total Alkalinity - now what?

[Bubbles]

Greetings to all

Glad to be a new member. I just openned my 19' x 44' 40,000 gal. inground pool. It came with a house I've been renovating and was a total wreck. I finally finished a complete rebuild last year - 30yds of concrete deck tearout, new beam band, stone coping, new concrete deck, replaster, all new pump & de filter - a 2 year project. In the end it turned out fine. So - this is it's second season & the 1st time I have openned a pool.

The chemestry was good @ end of season. I did a shock @ 12 - 13 ppm FC, drained & plugged the lines & put a solid tarp over it. Amazingly the water was clear when I removed the tarp yesterday. To be safe I shocked it again late afternoon - measured 12.5 ppm a w/low CYA of 10 or less 4 hours later. I use a Taylor K-2006 test kit.

Currently Ph is aprox 8. (FC still @ shock level) Total Alkalinity is 50ppm. The Taylor book calculates about a quart of Muriatic acid for Ph 7.4ish. and 2 lbs.of baking soda for TA 80-90. BTW - Calcium hardness is 260.

Finally my questions. Should I add the recommended adjustments? Should I wait til FC drops before I adjust? How can adding acid & base be the correct thing to do? Seems like they would cancel each other out.

Thanks for all help in advance!

Best regards from chemically challenged,
Charles

[PoolDoc]

Unfortunately, both the chemistry AND the terminology for pool pH and alkalinity is confusing. "Alkalinity" is sometimes used to mean "the pH is alkaline or above 7.0". But with respect to water chemistry, when the term "alkalinity" is used technically, it does NOT refer to water pH levels, but rather to the water's resistance to pH *change*.

Thus, water can be "acidic" -- low in pH -- and yet have "high alkalinity" -- high resistance to pH change.

Where it gets even more confusing is that most POOL alkalinity is based on carbonates, which tend to be active when the pH is higher and the water is "basic" or even "alkaline". So, while "alkalinity" in general is not necessarily associated with high, carbonate alkalinity is!

Confusing enough?

Let me make it simple. Taylor's book is the worst thing about the K2006, and like many other pool guides, creates the false impression that pool water chemistry can be managed like a recipe: 2 eggs, 1 cup of flour, 1/2 cup of milk -- mix with 1/4 cup of butter and pour into a hot greased pan for pancakes.

The problem is, recipes are for EVENTS, not for PROCESSES. Pool management is a process, not an event. For this reason, it's much, much more practical to follow the "test, adjust some, re-test, and adjust some more" PROCESS MANAGEMENT approach, then it is to follow the "test, calculate exact dose, dump and hope for the best" EVENT or RECIPE approach.

So . . . do this:

1. Lower your pH to 7.4 or so. You can try a quart of muriatic -- just keep dosing till you get there.
2. Then, add a dose of baking soda. If you want to start with 2 lbs, that's fine.
3. Then CONTINUE adding acid till your pH is OK, AND
4. CONTINUE adding baking soda till your Alk is high enough.

Get your pH in range ASAP. But otherwise, no hurry --if you get it all balanced in 2 weeks, that's perfectly fine . . . because you are managing a PROCESS, not an EVENT, and because plaster damage (if any) is very slow when the pH is between 7.2 and 7.8.

Realistically, you are probably looking at gallons of muriatic acid, and way more than 2 lbs of baking soda . . . but that's OK. READ the muriatic acid guide linked in my signature; get your baking soda at Sams Club or Walmart. (At both locations, it's less than $0.60/lb as "baking soda" but more than $1.50 as "alkalinity increaser"!)

[Watermom]

Good post above, Ben. Very clear explanation that will probably help a lot of people better understand pH and Alk.

[PoolDoc]

thx.

[Bubbles]

Great explanation & info! Many thanks!

Update: luckily I waited till I heard back. Glad I did. We had a few days of serious ran (4+") here in the Balt. Wash. area. My Ph dropped to 7.0 - 7.2 from 7.8 but I did add two 4lb boxes of baking soda. Numbers seem pretty good now. Ph is 7.4 & TA is 90. FC has slooowly dropped to about 7.5 ppm. No CC. I guess the water was pretty free if organics. Cya is up to about 30. Calcium hardness up to 320.

I guess it's best to leave well enough alone for now. Water is crystal clear. Thanks again for all your expert help.

Charles

[Watermom]

Looks pretty good. One comment I would make is that your calcium hardness is climbing pretty quickly. I assume you are shocking with cal-hypo. You want CH to be between 200-400. If it gets too high, you can have issues with cloudy water. So, you may want to switch to liquid chlorine at some point.

[Bubbles]

Thanks for the I input Watermom. Is Clorox bleach ok? Right now I have my chlorine tab dispenser turned off till the FC drops more.

Charles

[Watermom]

Yes, as long as it is plain bleach. No scented stuff, etc. Actually many of us use Walmart's generic bleach which is cheaper than Clorox.