How do I determine 'normal' for TA/pH balance

[Gigem94]

Hello TFPer's

I took over pool service, drained and refilled due to high CYA (thanks pool man!). I'm back on the steady maintenance and numbers (I think) and have a stenner maintaining chlorine levels and am using pinch a penny liquid bleach (10%). Pool plaster is prolly 7ish years in age. My question is how frequently I should expect pH to rise and how often to add acid. It seems with a TA of 90 that my pH of 7.6 goes up to 8 in about 2 days. No fill water or rain has occurred. No water features and no aeration.

Here are my numbers (I've been testing almost daily to understand the numbers and keep a log):
10/1 Reading (added 20oz of acid after reading)
FC - 5
pH - 8
TA - 90

10/2 Reading
FC - 5
pH - 7.6
TA - 90

10/5 Reading (added 20oz of acid after reading)
FC - 5.5
pH - 8
TA - 90

My fill water has a pH of 7 (or maybe lower as I cannot read below that) and a TA of 160, so after the refill in early Sept, I spent a while dumping a bunch of acid to lower TA, then aerating to bring pH back up. I got TA down to 80 and figured that was where it needed to be. So I am just trying to figure out what is 'normal'. If adding 14oz every 2 days in my normal, then ok, but I've read others hardly adding any acid at all on a routine basis. Just need some help in trying to determine what is my balancing point.

And a followup question, if adding 14oz every couple of days is normal (and for those folks who accept this as normal), do people actually get a stenner to do acid automation? That seems like a risky proposition to me, but I thought I'd ask.

Thanks for all of the awesome input!

 

[pabeader]

From my reading around the different threads, I see that as low as 50 is still considered 'normal' It really depends on your pH rise. As you have noticed, higher TA caused pH to rise quicker. I would say, keep pushing TA down until the pH rise is negligible.

Make sure you use Pool Math to watch the CSI range, so that you don't run into scaling issues.

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Folks with things like bubblers, fountains and other active stuff that cause pH rise will sometimes do a stenner type arrangement for MA additions.

 

[Patrick_B]

Focus on your pH first, always. You've already figured out how to lower the TA, and you're doing well with that. People like us will always have to add acid, and its just the way it is when you have high TA/pH makeup water. No getting around it, but acid demand will lower when your TA gets lower. Lots of users see an easier situation with a TA around 60 or perhaps 50. There isn't a magic number, you'll just have to experiment and see what happens in your pool. People that have low acid demand just have better water in terms of Alkalinity content. Most however are more like us with high TA, especially in this part of the country.

When you can maintain a mid 7 or slightly higher pH with far fewer acid additions, you'll know, but it will always be a fight. My makeup TA is pretty high at 130, but my pH is above 8, so I feel your pain.

 

[Cinic]

My fill water has a TA over 200 - so there is always upward pressure on my TA and pH.

My pH rise slows way down when I keep the TA in the 50-60 range. It won't really go over 7.8 or 7.9 unless the TA goes over 60. And it's a slow rise (4-5 days) from 7.5 to 7.8.

If I were you, I'd keep dropping the TA by 10 and see what happens. Yo will probably find a happy place somewhere lower.

 

[Gigem94]

Great feedback, thanks all. I'll keep dropping TA by 10 to try to find the sweet spot. Today I've gotta add makeup water (high TA, low pH) due to evap, so it's gonna take a couple of weeks. Will report back.

 

[duraleigh]

Going from 90 to 50 in 10 increments is problematic. The resolution of the test is 10 ppm so I suggest you simply bring it right on down with the acid/aeration method and not wait the month or more to drop it to 50 ppm.

 

[Gigem94]

Oh, so drop to 50 as quickly as I can and then see how it behaves. Makes sense, thanks Dave.

 

[kellyfair]

Lots of users see an easier situation with a TA around 60 or perhaps 50.

This is me. My TA is 60, and my pH literally has been at 7.5 all summer long - never changes!

 

[Gigem94]

OK circling back on this topic, my TA is nearing 50. So I am curious, what do I do if the pH rises above 7.8 with a TA of 50?

 

[pabeader]

Limit the use of the spillover. With that running, it will eventually rise up there. You might want to let it though, at least for a day or two. It might actually settle in there and not go any higher. If it does, you can always knock it back down with a little MA.

 

[Gigem94]

So my spillover does not create any bubbles, it's just more of an overflow from the spa to the pool: Mike has shared 1 photo with you! | Flickr

I guess what you are saying is the amount of acid required to drop the pH from say 8 to 7.6 should have a minimal effect on TA, right? And I should just closely monitor TA before I do.

 

[abycat]

I run 60-70 ta in my pool and don't use barely any acid but the tub eats quite a bit even with a 50-60 ta. I sure notice my pool and tub are quite a bit different than every other pool.