UPDATED - PH Issues

[Cayman]

I have got most of my chemicals under control but I am still having problems with the PH rising all the time. I will check it one day and it will be 7.6, then jump to 8.2 the next day or so. I read that water features make the PH rise but even tried shutting the waterfall off and still have the same problem.

Also, for some reason my CH climbed recently. Could adding Boarx contribute to this?

Latest test numbers are in my signature.

Thanks.

 

[duraleigh]

Re: PH Issues

Almost all pools with an SWG are subject to constant pH rise. As you probably know, muriatic acid will control it.

Do you suspect some other reason?

 

[Cayman]

Re: PH Issues

No not really. Just thought adding over a gallon a week was excessive. LOL

 

[JasonLion]

Re: PH Issues

Adding borax will make the PH rise at the time that you add the borax. However, borax that is already in the water will slow down (buffer) PH changes caused by other sources.

Your TA is a bit too high. That will cause the PH to rise, particularly when there is aeration (which can come from the SWG as well as the waterfall). However the PH increases you describe are quicker than I would expect from TA around 120. And none of that would explain the CH increase.

Is there anything else you have been adding to the pool recently (fill water, other chemicals, etc)? Or any unusual occurrences?

 

[Cayman]

Re: PH Issues

Nope... I have topped the water off a couple of times but that is it. Oddly enough our entire house including outside hoses all have soft water from the softener. I have tested the CH and it is 0. Anyway, I only ran the hose for 15 minutes or so each time.

Other than adding the Boarx, then countered it with Acid... that is all that has been done.

 

[chem geek]

Re: PH Issues

Just add acid to bring the pH down and everytime you do that the TA will get lowered some as well. In fact, if you were truly adding one gallon of full-strength Muriatic Acid (31.45% Hydrochloric Acid), then this would have the pH drop from 8.2 down to 7.3 and the TA would drop from 120 ppm down to 90 ppm. After that, the pH would then rise. So your TA should be dropping by around 30 ppm per week if you were adding a gallon of acid every week. That implies that you have been adding baking soda or Alkalinity Up to raise the TA -- is that correct?

I would suggest you get the TA down to 80 and not add anything to raise it unless you still find you need to add a lot of acid to lower the pH. With 50 ppm Borates, it's very surprising to find such a large pH rise still occurring so quickly, especially after turning off all the waterfalls.

If you don't have a lot of sunlight and if your SWG is already set fairly low, you could see what happens if you turn off the SWG for one day. If you find the pH rise to still occur, then it's the higher TA plus other aeration sources or some other mystery. If you find the pH rise to significantly slow down, then the SWG is the main culprit, possibly from outgassing chlorine gas in which case I would ask whether the SWG is very close to the pool itself (i.e. short return lines) and whether the returns are pointed up, straight or down.

The CH could rise if you've got a lot of evaporation and your fill water is high in CH. You can test your fill water to see. Perhaps the TA in the fill water is also high and helping to keep the TA from dropping quite as much, though it would take a heck of a lot of evaporation for this effect to be very noticeable in a short time.

Richard

 

[Cayman]

Re: PH Issues

Richard -

Thanks for the reply. I have only used Acid and Borax in my pool. The acid that I have been using has been in-between adding the Borax so maybe that is why my TA is where it is. The Borax is now set so going forward may give me a better idea but it looks as if I am going to drain and refill some water to get my CH down thus causing me to add more Borax.

The pool does get a bunch of sunlight and has no trees around it at all. The current setting of the SWG is 10%. That seems to be the magic number right now. I bumped it up to 13 and my FC went to 6 so I dropped it back to 10% last night.

The SWG is roughly 50 feet from the pool. Maybe lightly less but that would be a close estimate.

As previously noted, the CH of my fill water is "0". My water softener is plumbed on the main line prior to it entering the house. This is the only way my install guys does them. As far as evaporation, it has not been much as all. Like I said, I have only topped it off twice for about 15 minutes each time in the past month.

I will bring my TA down to 80-90 and then keep an eye on it from there. I will be sure to let you all know what I find out from there.

Thanks.

 

[Cayman]

Re: PH Issues

OK... I am a little puzzled here. I was looking at the affects of certain things on the pool calculator and here is where I am lot.

If I get my TA to 80 then when my PH rises from either the SWG or Aeration, what do I do to lower the PH without effecting the TA since adding Acid lowers PH and TA???

 

[Malcolm]

Re: PH Issues

How old is your plaster? It's my understanding that for the first year curing plaster will contribute to pH rise. In fact, my plaster is about five months old and I'm still adding about a quart of acid a week even with my SWG turned off.

 

[JasonLion]

Re: PH Issues

With borates in the water and a SWG we generally recommend lowering your TA further, down to perhaps 50 to 70. This will dramatically slow the rate at which the PH goes up and also help compensate for the high CH levels.

While lowering your CH level, to say 300 to 350, is a good idea in the long run, I wouldn't put too much effort into lowering it quickly. Getting your TA down will lower your calcite saturation, eliminating any hurry in getting your CH down.

When PH rises you do need to lower it with acid, and that does also lower the TA. To compensate for that you will need to add some baking soda now and then to bring the TA back up. However, as your TA gets lower the rate of PH increase comes down and you end up adding less and less acid. When things stabilize at a lower TA level the frequency of needing to raise your TA will be greatly reduced and you will probably only need to raise TA two or three times a season.

Malcolm is also correct, that in the first year of new plaster the PH will rise from the plaster curing regardless of everything else we have been discussing. This effect can be very dramatic in the first three or four weeks of new plaster, and then continues at a lower rate for the rest of the first year. Fresh plaster will also cause the TA and CH levels to rise significantly, which could account for everything you have been describing.

 

[chem geek]

Re: PH Issues

DOH! I always seem to forget about new plaster. Yes, that would explain a lot. In fact, if there were no outgassing at all, then one gallon of acid in this 16,500 gallon pool would compensate for curing of concrete that raises CH by 30 ppm. The TA would be stable in this case (when measured at the same pH) so the net result that would be seen would be adding acid and rising CH with the pH rising between acid additions.

On the other hand, I can't find anything in Cayman's posts that talks about a new pool or a plaster refinishing. I must have missed that.

 

[JasonLion]

Re: PH Issues

From previous posts, the pool was "pretty new" back in September. First three or four weeks seems out of the question, but first year seems likely. Hopefully Cayman can clarify soon.

 

[dschlic1]

Re: PH Issues

From my experience, curing plaster can demand a lot of acid for a very long time. In my case I the plaster was a year old, and I was still adding a quart of acid per week. So for a year I was adding one quart of acid per week for a 7500 gallon pool. TA remained virtually unchanged. CH did climb.

A couple of months ago, I did the TA reduction procedure. Interesting, after this procedure, my acid demand dropped to one pint every two weeks. However my CH shot up.

 

[Cayman]

Re: PH Issues

I guess the age is about the only thing I have not put in my Signature. LOL The pool is 2 1/2 years old.

Well thanks for the information and clarification. I will get the TA down and then watch it from there.

Thanks again guys... I will post the results of my PH and TA tests over the next couple of days on this thread.

 

[Cayman]

Re: PH Issues

OK... I tested the pool this morning (which I normally test in the evening but did not have time last night) and my PH is down to 7.4 after my dose of acid the other day and my TA is down to 100. So should I let the PH come up some naturally and then dose with Acid again to to drop the PH and TA. Then continue until my TA is to the desired reading, correct?

On another note, my FC was 2.5 this morning with 1.5 CC. The reading seemed low on the FC but I was thinking it was due to me checking in the morning. I am not sure about the CC though. Last time this happened, I had an algae problem. But right now the pool looks perfect so I am not sure. I will check this again tonight just to be sure. Any thoughts on this?

 

[JasonLion]

Re: PH Issues

So should I let the PH come up some naturally and then dose with Acid again to to drop the PH and TA. Then continue until my TA is to the desired reading, correct?

Yes. You can either wait for the PH to come up by it's self, or you can aerate the pool to speed up the PH increase.

On another note, my FC was 2.5 this morning with 1.5 CC. The reading seemed low on the FC but I was thinking it was due to me checking in the morning. I am not sure about the CC though. Last time this happened, I had an algae problem. But right now the pool looks perfect so I am not sure. I will check this again tonight just to be sure. Any thoughts on this?

You do not want CC to be above 0.5 at any time. Hopefully that reading is just testing error and it will be back to normal this evening. If you really have CC of 1.5, and haven't added any MPS recently, you will need to shock the pool to get rid of the CC.

 

[Cayman]

Re: PH Issues

We have had unually high temperatures lately... mid 70's to low 80's for a month or so now. Recently we had a couple of days with high winds and I notice a fair amount of pollen on the tile line. Just thought I would add this for some additional help.

 

[Cayman]

Re: PH Issues

I tested again last night and there are 0 CC so I guess all is good!!!

I will let the PH rise to about 7.8 an then dose again to bring it and the TA down. I will continue to do this until the TA gets down to 70-80. Hopefully this will work.

 

[Cayman]

Re: PH Issues

Well I used the Pool Calculator to let me know how much acid to add and added it. PH stayed nice for a while and TA was down to about 90. Well now the PH is back up to 8.2 and the TA is back up to 130!!! (I will upate the numbers in my signature tonight)

I have not added anyting or changed anyhting but we did have a large amount of rain which caused me to have to drain a bit of it. The rain filled the pool to over the top tile. Could this have caused the jump in both?

 

[JasonLion]

Re: PH Issues

Rain often changes the PH. It is much less common for rain to change the TA, but that has been known to happen.