PH Levels after Newly Plastered Pool

[markphin]

Hello All,
I've seen lots of good threads regarding this subject. But, here's my issue/question.
I had my pool replastered with an exposed aggregate(krystal krete) back in early May. Came out great and have been staying on top of my Chemistry(mostly adding acid to keep PH down). Currently I am adding a little less that a gallon a week to a 30,000 gallon pool(adding 16-24 oz. every other day or so). Any ideas on how much longer I will have to add acid before things start to stabelize. My concern is that when I go to winterize and cover it this fall and the PH is still driving up, what will I open up to in the spring.

Thanks in Advance!

[chem geek]

You should post a complete set of water chemistry numbers for Free Chlorine (FC), Combined Chlorine (CC), pH, Total Alkalinity (TA), Calcium Hardness (CH), and Cyanuric Acid (CYA)from a proper test kit, the Taylor K-2006. Your TA may be too high and contributing to pH rise. You may also be lowering the pH too much when you add acid since lower pH also outgases more carbon dioxide that has the pH rise.

Plaster curing has the most pH rise in the first days, then slows down over weeks, and after months the effects from TA should outweigh those from plaster if it was properly sealed. If you had an acid startup, it may take longer for the pH to settle down compared to a traditional startup or the best which is a bicarbonate startup. The latter seals the plaster in-place with virtually no plaster dust nor rise in CH.

[markphin]

Thanks for the quick reply. I will get numbers posted later this week. I do keep the TA in check. In fact I had to add some TA up to bring levels back with in range last week. Thre was no special start up method used. But when they finished plastering they did a light acid wash to expose the aggregate. Perhaps that is contributing.
Thanks Again

[CarlD]

Thanks for the quick reply. I will get numbers posted later this week. I do keep the TA in check. In fact I had to add some TA up to bring levels back with in range last week. Thre was no special start up method used. But when they finished plastering they did a light acid wash to expose the aggregate. Perhaps that is contributing.
Thanks Again

I hope you realize that TA Up! is nothing more than ordinary baking soda. If it says Sodium Hydrogen Carbonate, you should know that's an alternate name for Sodium Bicarbonate....Arm&Hammer Baking Soda! And, if you use pH Up!, you'll see it's Sodium Carbonate--same thing as Arm&Hammer Washing Soda (In the yellow box in the laundry section).

[chem geek]

Also, what is the "range" you are talking about when you write "to bring levels back with in range"? Pool industry standards are NOT correct and when using hypochlorite sources of chlorine (e.g. chlorinating liquid, bleach, Cal-Hypo, lithium hypochlorite) you want your TA lower, even lower than 80 ppm if necessary to have the pH be more stable. This is because TA does not just buffer pH, but is a SOURCE of rising pH in its own right because TA is largely a measure of how over-carbonated water is compared to air.

[markphin]

The TA was 70. So I added enough to bring up to 90. I see what you are saying though. Keep the TA at lower levels and it will help control the PH. Thanks I will keep an eye on that. Things do seem to be slowing down a bit more. Over the last 5 days I've only added about 2 quarts of acid, when up to this point I was adding about a gallon a week.

[CarlD]

The lower TA should help. As the concrete cures the rising pH should end. Do you have anything like a waterfall or fountain or other water effects? They all create aeration which tends to raise pH (but doesn't raise TA--that's why we use it in our TA-lowering strategy).

[markphin]

No fountains. A spillover from the hot tub though. Yeah, I'm sure the PH will stabelize eventually. I just didn't think it would take this long. I'm hoping it stabelizes by the time I winterize in another month or so.

[CarlD]

The spillover could well be part of the reason for a rising pH, because it will aerate the water.

[markphin]

I kind of doubt it, as prior to the replastering, I have had little rise in PH over the couse of the previous 13 years. If I put a gallon of acid in a summer it was a lot. I think its primarily due to the curing of the new plaster. Perhpas the aeration is adding to it a bit though. I guess I just have to be patient and wait it out. Hopefully not to much longer though.

Thanks

[Shifty]

@markphin: I am about 5 weeks post a re-plaster with krystalkrete. For the first 3-4 weeks, I was adding a similar amount of muriatic acid as you were. I was brushing the surface twice a day; however, a lot of the plaster dust was staying in the deep end near the main drain. Once I hit the 30 day mark and used my pool vac, I was able to vacuum any excess plaster dust. Since removing the plaster dust, the pH has stabilized. While the plaster continues to cure over the next 6 months, I still expect the pH to slightly fluctuate.

Make sure to test your water regularly.

Have you seen your pH stabilize? I realize this thread is almost a year old.