pH STAYS at 7.9

[fre1102]

18k gal. chlorine plaster pool. Taylor liquid test kit. Replastered about 60 days ago. TA is at 70, trending down from 80 over the last two months. I expect TA to go below 70 soon.

Subject is pretty much it. Pool stays at 7.9. I can get it down to 7.8 on occasion and it'll go over 8.0 if I go a few days without adding acid.

Every morning when I test I add acid to get back to 7.6. I'm about to go add acid this morning and I'm sure if I test again this afternoon after adding acid it'll be back at 7.8-7.9. I was testing about four hours after adding acid for a few days and same result--7.9-ish when I test, add acid to get to 7.6, four hours later...7.9. I'd worry that I'm colorblind except I had one test, once, at 7.6...week ago. I'm looking at the tube in sunlight at a white (or off-white) background. I'm starting to think I'm just testing wrong. For a while I thought I was just insane and if I did nothing it'd stay at 7.9, but no, it will creep up past 8.0 if I don't keep acidulating it.

Reagents are not expired, acid is new.

I don't want to damage the plaster, and the pool is fine to swim in. Is there a drawback to just letting it stay at 7.8-7.9, or do I need to keep plugging this thing with acid every morning? I'm starting to worry that all I'm doing is leaching the plaster and I should just let it ride until next year and it's completely cured.

 

[Texas Splash]

Is there a drawback to just letting it stay at 7.8-7.9

Depending on water temp and CH level, possibly calcium scale build up. The pH test kit a bit challenging. Not my favorite either. When you lower the pH, are using the PoolMath APP to help determine the amount of acid required? Are you trying to lower the pH down to say 7.2 or 7.4? Have you tried that yet? I find that by seeing a true pH in the orange (say 7.4-7.5) really helps you eyes to adjust to the colors because IMO the upper 7s to 8.0 range becomes a lavender blur.

 

[Texas Splash]

You can let the TA fall down to about 50, but no lower. Also be sure there is no aeration in the water which can cause the pH to rise as well.

 

[fre1102]

Depending on water temp and CH level, possibly calcium scale build up. The pH test kit a bit challenging. Not my favorite either. When you lower the pH, are using the PoolMath APP to help determine the amount of acid required? Are you trying to lower the pH down to say 7.2 or 7.4? Have you tried that yet? I find that by seeing a true pH in the orange (say 7.4-7.5) really helps you eyes to adjust to the colors because IMO the upper 7s to 8.0 range becomes a lavender blur.

Yup, using the app to determine amounts to add. For a while about a month ago I was trying to get to 7.2 - 7.4 both to see if I could but also because either the app (pre-update) said that was the ideal range, or because I read it online (I forget which). I *can* get it lower if I add enough acid, I just quit because I was worried I was leeching the plaster and now the app says 7.6 is ideal.

Mostly I'm amazed at its rebound-ability. Clearly the acid IS acid (I thought maybe it was old or a bad batch) and it is acidulating the water. It's more that very, very quickly the pH creeps back up to the 7.8 - 7.9 range and then seems to stay there a while before creeping up again more slowly after that. It's like the pool wants to be at 7.8 - 7.9.

I agree about the color tests--it's all just 'blue' to me at some point. And it doesn't help that I'm either looking for a cloud to hold the tube in front of or else trying to hold a white towel behind it, or whatever.

 

[Texas Splash]

Perhaps your plaster is still doing a tiny bit of curing. I wouldn't be surprised. FWIW, my FG pool often times likes to settle around 7.7-7.8. I suspect you have the CSI tracker enabled in your Poolmath settings? As long as your CSI is slightly negative you should be fine. Speaking of Poolmath, you can go into settings and select the option to link Poolmath test logs to your TFP profile, that way we can see all of your numbers.

I'll pass along your concerns about the APP to out admin folks.

 

[fre1102]

Perhaps your plaster is still doing a tiny bit of curing. I wouldn't be surprised. FWIW, my FG pool often times likes to settle around 7.7-7.8. I suspect you have the CSI tracker enabled in your Poolmath settings? As long as your CSI is slightly negative you should be fine. Speaking of Poolmath, you can go into settings and select the option to link Poolmath test logs to your TFP profile, that way we can see all of your numbers.

I'll pass along your concerns about the APP to out admin folks.

I haven't even figured out how to see my testing history in the app yet. It'd be cool if I could see XX date and test results going back over time. I kept a notebook for a month or so, now I'm just going on memory.

 

[Dirk]

My personal experience...

Worry less about pH and more about CSI. If your CSI is within range, then your plaster will be fine. My pH rides around 7.8, which keeps my CSI at around -0.3, which is ideal for a saltwater plaster pool running an SWG. If you don't have a saltwater chlorine generator, then a CSI of 0.0 is ideal.

When I first came onboard here, I was determined to keep my pH at 7.5, because I had it in my head that 7.5 was the pH of my eyes, and so a pool with pH of 7.5 would be most comfortable for my eyes. So I struggled, just like you are, to force my pH down. Well, that just doesn't work. Pools seem to want to find their own pH, and the more your try to force it down, the quicker it bounces right back. That's pretty much normal. And it's not a direct ratio, it's logarithmic. By that I mean, trying to get from 7.9 to 7.7 won't take twice the acid as going from 7.9 to 7.8. It'll take more. 7.9 to 7.6 will be all that much more, and 7.9 to 7.5 or lower even more! (As you've probably already discovered.)

Eventually I focused on CSI instead. I now fill my pool with soft water, to keep my CH in the 350-400 range, which allows for a pH of 7.8 or 7.9 to maintain a CSI of -0.3. Everybody is happy, and my eyes feel just fine! Plaster is doing well, and because my CSI is a little on the negative side, I haven't had a spec of calcium deposit develop on the plates of my SWG or anywhere underwater on my plaster.

To address the regular acid handling, I installed an automatic acid dosing system, so I only have to handle acid a few times a year now (to fill the machine). And because my acid dosing happens once every hour, my pH is pretty much dead-on all day long, week in and week out, without me having to add any myself.

 

[fre1102]

My personal experience...

Worry less about pH and more about CSI. If your CSI is within range, then your plaster will be fine.

When I first came onboard here, I was determined to keep my pH at 7.5, because I had it in my head that 7.5 was the pH of my eyes, and so a pool with pH of 7.5 would be most comfortable for my eyes. So I struggled, just like you are, to force my pH down. Well, that just doesn't work. Pools seem to want to find their own pH, and the more your try to force it down, the quicker it bounces right back. That's pretty much normal. And it's not a direct ratio, it's logarithmic. By that I mean, trying to get from 7.9 to 7.7 won't take twice the acid as going from 7.9 to 7.8. It'll take more. 7.9 to 7.6 will be all that much more, and 7.9 to 7.5 or lower even more! (As you've probably already discovered.)

keep my CH in the 350-400 range, which allows for a pH of 7.8 or 7.9 to maintain a CSI of -0.3. Everybody is happy, and my eyes feel just fine! Plaster is doing well, and because my CSI is a little on the negative side, I haven't had a spec of calcium deposit develop on the plates of my SWG.

To address the regular acid handling, I installed an automatic acid dosing system, so I only have to handle acid a few times a year now (to fill the machine). And because my acid dosing happens once every hour, my pH is pretty much dead-on all day long, week in and week out.

I'm Googling CSI now.

I spent a day or two trying to back into what the app was doing in my head before I quit and decided to just trust its math. What made that worse for me were the subjectivity errors--if I think the color is at a 'soft' 8.0 (let's call it a 7.95) that's disproportionately (intuitively) more acid to bring it down (because pH is logarithmic, like you said) that if I just call it a 7.8. There was frustration.

My CH is about 200. The pool store said to keep it there and the sheet the plasterers have me has the copy cut off in the CH section. You're at double my levels--should I be reconsidering my CH?

You've got an automatic acid-adding system? That sounds like a great idea. Did you buy that or build it yourself?

 

[Dirk]

Rule number one, which I similarly had to learn the hard way: don't mix and match your pool advice! Don't "google" CSI, learn about it here at TFP. And don't do ANYTHING a pool store tells you to do.

Job 1 is to fill in your signature. Something like mine is especially helpful to the guides and experts here that will help you. Edit your signature first.

Then study this page, here at TFP, about recommended levels. TFP is not some random google site, nor is it a collection of pimply-faced teens or untrained "managers" that you'll find at a pool store. Our method and recommendations are based on science, decades of it, all torture-tested across HUNDREDS OF THOUSANDs of pools, all over the planet. Pick ONE source of advice, follow it to the letter, and that should be TFP if you want to have long-term success with your pool.

The only caveat to the above is to honor your plasterer's/builder's chemical spec if you want to keep your warranty intact. Often, these specs conflict with our advice, and we can prove that these conflicting specs are going to be bad for your pool, but that might not outweigh the financial impact of maintaining that flawed spec to protect your warranty. That's a call you'll have to make. You should get another copy of the spec from your plasterer, so that we can better determine where you need to be at CH-wise. If they're spec'ing a CH that fits within TFP's guidelines, then you're golden and we can then correct your CH appropriately.

Regarding my automatic acid-adding system, it is a Pentair IntellipH. It is a companion to, and relies upon the presence of a Pentair IntelliChlor Saltwater Chlorine Generator (SWCG or SWG). You cannot run an IntellipH without an IntelliChlor. But there are stand-alone acid dispensing systems that are available, should you want to explore that path.

 

[Dirk]

Basically, CSI is an index, that is calculated from the test results of your other pool chem levels, that will help you determine if your pool water will tend to be corrosive to your plaster, or allow your CH to build up (scale) onto your plaster. CSI within our recommended range will be best for the long-term health of your plaster. Here's the details/science behind it:

CSI and LSI - Further Reading

www.troublefreepool.com

CSI is automatically calculated by TFP's Pool Math app. You have to turn it on in the app's settings to see it.

 

[Bperry]

You've got an automatic acid-adding system? That sounds like a great idea. Did you buy that or build it yourself?

Wait for your TA to get down around 60 and you’ll find the acid demand slow down a lot. The acid dispenser sounds great when you’re battling with it but once it slows down, i think you’ll find the need for it goes away.