Algae, TA or what?

[CarlD]

"Covered"?

I use my solar cover (though not the last few days as the heat has been extreme) but do leave it off. It doesn't seal, of course.

Current TA is 80 so I guess I'll leave it there. pH hasn't moved from 7.6 all summer (it's usually 7.5 in past years). TA doesn't usually move much on me either. CYA is just under 50, FC is around 5. CH is pretty low--I don't measure it more than once or twice a season. I THINK it was 110 or 120. I have no real source of cal since I haven't used Cal-Hypo in a few years.

I generally use a higher qual LC that claims 12.5% but always tests at 14% (never thought to test the pH).

Normally, I add about half a gallon every other day, but lately, with the heat, I've been using more. In fact, this season, like almost everyone, I've used far more chlorine than usual. I've just drained the first gallon off my 5th carboy of the summer, and it's only early July. 5 is normally a full summer's worth.

I realize you are not "there" yet, but we are going to need practical guidance regarding TA levels "If you pH is this, and your FC is this, and...., and ...., then do THIS."

Thanks for all your hard work.

Carl

[sturev]

Hi Guys,

I'm willing to help if you want it. I have a unique pool that may help prove/disprove theories???

My pool is fully insulated and covered, it stays at a constant 88 degrees and is subjected to maybe an hour or so of sunlight a month (exercise in the evenings & the sun is off the pool). I have no CYA added to the water. I would think it would be considered a heavily aerated pool, as the counter current alone creates a lot of air bubbles and then put me in there flailing around trying to swim upstream ; the whole pool is filled with air bubbles for about 30-40 mins a day.

I've only used the BBB method on a fresh fill about 2 months ago. I have added a total of one box of Borax, 1/2 gal of Acid and 1.5 gal of bleach since the refill. I run FC between 2 & 4; only have to add 6 oz every 4 or 5 days. Right now my TA is on the high side (150; was 230 on fill and I've been working it down in the last few weeks). PH is 7.8, until I add acid to bring down the TA; it takes 48 hrs to go from 7.0 to 7.8.

Let me know if I can be of any help...

[Furbabyvet]

FWIW, I'm keeping the solar cover on the pool now and the pH seems to be rising more slowly, not to mention the chlorine disappearing more slowly. I just wish it didn't make it feel like you're swimming in a nice, comforting bowl of tomato soup . Gotta get a solid color cover...

[PoolDoc]

@ Sturev: thanks for the offer. I'll try to keep that in mind -- I'm working on some plans, now for research, writing, and PoolForum development.

@ Furbyvet: thanks for the info. Your response represents a confirmation of Chem Geek's analysis of TA and pH rise in pools.

Ben

[waterbear]

The following comments are just my own opinions based on my own experience and study. Take them for what you think they are worth:

Hey Guys;

I'm missing some things here.

Waterbear, I'm not clear on your thinking about TA. You may have some really good reasons behind your thinking, but right now, I'm kinda puzzled. Do you have reason to think that lowering Alk will reduced acid demand or pH rise? Have you seen evidence that a really low Alk (below say 50 ppm) is OK for a plaster pool? Why did you feel that lowering Alk was more important than dealing with her algae?

First, I was suggesting several things that can help with rising pH since the original question was about pH control and the algae problem was mentioned as a secondary one. I was giving several general recommendations at controlling rising pH that I have personally seen work. I did make the assumption that the OP was chlorinating with bleach when I suggested dropping the TA a bit since the OP said they had been doing BBB for two months. Lowering the TA will lower the rate of outgassing of CO2 if that is the cause of pH rise. The chemistry is here:
http://www.poolforum.com/pf2/showpos...34&postcount=2
although I was relating it to the lowering TA process.

I personally have never recommended lowering the TA below 50 ppm but I have found that lowering it form 80 to 60 ppm can often have a positive effect on pH stability when using an unstabilized chlorine source, which is basically pH neutral. Higher TA is really only beneficial with stabilized chlorine sources, which are acidic in nature and benefit by the tendency of the carbonic acid/bicarbonate buffer to raise the pH toward 8.2.

Also, the addition of borates will tend to move pH down and can (and does)help with rising pH in most pools and reduces acid demand (Chem geek disagrees and says that total acid use will stay the same but I have seen a reduction in acid use in my pool and in customers pools). The algaestatic effects of borates have been demonstrated to me sufficient times for me to recommend them as a useful pool additive and one that is really beneficial in pool with a SWG, where the reduced chlorine demand can translate into better pH stability because of less on time of the salt cell.

As far as SI, as 'useful' as it is, if the CH is around 350 or so and other water parameters are in the 'normal' ranges and the pH is kept at 7.6 or above then the water will still be in 'balance' with a TA around 60. Certainly in the ballpark, given the precision of our testing and the accuracy of most pool volume measurements. Chem geek gave you the hard chemistry in his post so I don't need to go through it a second time.

My recommendation to not lower pH below 7.6 is to slow the outgassing effect and you commented on it in a recent post that you had observed the same effect on pH and acid demand:
http://www.poolforum.com/pf2/showpos...7&postcount=23

I did also address the algae problem and made some generalize suggestions since, at the time, it was not clear that the algae was embedded in an aggregate finish above the water line and my thinking was that the pool might have been receiving a lot of sun and would benefit from slightly higher CYA levels given the AZ location and that there simply was not enough chlorine staying in the water to keep the algae at bay.

CarlD, are you aware that chlorine becomes less effective against algae as pH increases? The most dramatic problems are with unstabilized chlorine, but as best I can make out, the problem is still significant in stabilized pools, too. Since she reported that her pH was tending to go ABOVE 8, it's my opinion that that's an issue that needs to be addressed in the short term, in addition to raising the chlorine.

I don't intend to speak for CarlD but I do understand where he is coming from. Chlorine kills algae and that is all a newbie needs to keep in their head. Unless the other parameters are WAY out of whack sometimes it's better to leave adjustments until the algae is dead. One thing I learned by working in a pool store is KISS. Many novice (and old time) pool owners cannot multitask so you have to decide what is the most important thing to deal with first. Using just one chem at a time is often the best way for them to do what is needed to solve a problem, even if it is not the most "efficient".

Chem Geek has done some stuff with 'carbonics' that I haven't had a chance to digest, or much less fully consider yet. However even once I do, I'm not prepared to toss out all S.I. considerations without some experimental verification first. Stoichiometry is nice, and successful process chemistry often resembles the stoichiometric analysis, but rarely is identical with it.

FWIW, I find his recommendations and chemistry sound and tend to agree with him. Then again I have not had access to test pools so my observations supporting him are just the empirical evidence I saw in customer's pools (and my understanding of the underlying chemistry). A limited sample in one part of the country at best!

I'm leaning toward stating some 'standard' recommendations for Pool Forum responses, but I'd like to see what y'all have to say, first.

As always, thanks for all your help.

Ben
"PoolDoc"

Standard responses are a good idea but I would not let them get so rigid that they become 'Laws' that get repeated without understanding and mistinterprented too often as they did on a different forum. There is always an exception to the rule, is there not?
IMHO, they should be set up as guidelines but each pool really does need to be taken on a case by case basis IRL.

[CarlD]

I can't imagine us getting rigid beyond belief on items of pool chemistry. There are LOTS of ways to get things done--remember Ben's attack on a high calcium pool by using lots of cal-hypo directly through the skimmer (or something like that). I STILL have no idea what that was about but it worked!

(OK, maybe when it comes to adding calcium to a vinyl pool with a bloom we are going to be rigid and say "Save your money. It won't help!")

[chem geek]

Also, the addition of borates will tend to move pH down and can (and does)help with rising pH in most pools and reduces acid demand (Chem geek disagrees and says that total acid use will stay the same but I have seen a reduction in acid use in my pool and in customers pools). The algaestatic effects of borates have been demonstrated to me sufficient times for me to recommend them as a useful pool additive and one that is really beneficial in pool with a SWG, where the reduced chlorine demand can translate into better pH stability because of less on time of the salt cell.

My comments on the borates having no effect on total acid used, just on the rate of pH rise (so acid is added less frequently, but more needs to be added to move the pH) are based on borate buffering that does not outgas carbon dioxide. However, if waterbear sees a real effect of acid reduction, then it is always possible that the borates affect the rate of carbon dioxide outgassing, perhaps related to their lowering of surface tension in the water or some other effect inhibiting the facilitated transport near the water's surface. In my own pool I haven't seen the total acid change, but my pool is covered most of the time so that only some of the pool's pH rise is due to carbon dioxide outgassing. We'll need to track more users to see the effects. I know that there are some who have added borates and not seen benefits in their pools with regard to acid addition and in some cases even in the rate of pH rise (which doesn't make sense).

Richard