Alkalinity and PH issues

[Krizoid]

I just set up my first pool this year, a 25k gal above ground. Filled with my well water. After filling and filtering out a lot of iron with the DE filter the PH has continued to rise. At latest test PH was 8+ (8 is the limit of my taylor kit). I'd like to balance the water but my fill water is pretty high in TA.

the well water is
350 Alk
350 CH
7.4 PH


My biggest goal is to control the PH and not be always fighting it. I understand the bicarbonate to carbonic acid buffering and how the carbonic acid will equalize with the air. The PH tends to rise over time which my research seems to say it due to carbonic acid off-gassing as Co2 over time leaving a net increase in bicarbonate behind to raise the PH.

What I haven't been able to confirm is if lowering the total alkalinity would cause the PH to stay in the acceptable range (assuming no addition of chemicals). If I lower the TA to the correct level, will the PH tend to stay within the 7.2-7.8 range or am I destined to always be adding acid?

I guess I also have a second question. Adding Muratic acid is listed as the solution to both the high PH and high alkalinity. On poolsolutions.com it says that adding acid to a low PH and aerating is the only known way to lower alkalinity if the fill water is also high in TA. It also mentions this is very counter to the conventional wisdom. What I am read on many sites is that to reduce alkalinity you simply add acid (without the need to aerate or go to the lower part of the safe PH range). I don't understand the difference between both methods. Why would merely adding acid without aerating send you on a "roller coaster ride"? I would expect that lack of aeration would mean that the offgassing to Co2 would just be very slow resulting in a slow PH rise and a slow reduction in Alkalinity.

Hopefully I've asked intelligent questions and given enough background data in this rather lengthy post.

[Watermom]

Just checking to see if you are still around and still need some help.

Sorry that you never got a reply. We had lots of new members who all registered in a short period of time that we got behind. Hopefully we are about caught up.

So, if you still need some help, reply back and someone will try and give you some advice.

Welcome to the Pool Forum, by the way!

[PoolDoc]

membership upgraded.

I think this page:
http://www.poolsolutions.com/gd/lowe...p-by-step.html
will answer many of your questions.

Basically, you just need to keep your pH at 6.8 - 7.0, till your carbonate alkalinity drops to whatever arbitrarily low level you'd like -- 80 ppm?.

Since you've read what's on other sites, and in the pool literature, I probably need to say this: my sites (PoolForum and PoolSolutions) and a now-larger 'offspring' site (TroubleFreePools.com) are the only sources I know that give a correct explanation. I worked this out about 20 years ago, and have since discovered that this process (off-gassing to lower carbonate alkalinity) is well known in the potable and waste water treatment business, and is also understood by some aquarists. But, even after 20 years and 10,000's of successful applications, the pool industry as a whole still embraces the nonsense approaches you've encountered.

You may be understandably skeptical: all I can see is, try it and you'll become yet another data point verifying this approach.

[Krizoid]

Thanks for the replies, I was beginning to wonder if I had posed an unanswerable question. I have been doing the alkalinity reduction method in your link for a week now and my alkalinity is down to 130. I plan to continue until I am in the 80-100 range.

This seems to be a related question in my mind. Will my PH stop drifting up to 8+ when the alkalinity is lower? or will it drift more slowly? or will it just take less acid to bring it back down? Obviously I've been keeping PH low to reduce alkalinity so I am wondering what to expect when am done.

Lastly I have had a tough time getting a good answer on why I need to maintain a pool at PH <7.8. Do you know of a link or paper that explains why a high PH is a problem. I'm interested in a technical explanation and not afraid of chemical equations.

At this point my questions are more for my own understanding. I just want to know why I am doing things to the pool not just what to do.

Thanks,

[PoolDoc]

Will my PH stop drifting up to 8+ when the alkalinity is lower?

Yes.

Lastly I have had a tough time getting a good answer on why I need to maintain a pool at PH <7.8.

Chlorine becomes less active as the pH goes up; water balance (pH + calcium hardness + alkalinity) becomes harder to manage; you'll have to buy a pH meter to manage things.

That's a very, very brief explanation that over-simplifies things, but is correct practically speaking.

If you want more, I'll put you in touch with all the work Chem_Geek has done -- but understand you don't need to know, to do your pool well.