Why does my pH need to be in the 7's?

[chiefwej]

A bit of background. I have a SWG and my fill water is usually high TA and high CH. Before finding TFP I had problems with rising pH and consequently scale. After some study, I lowered the TA and added borates to help with pH rise. I began closely monitoring and controlling my CSI to prevent any future scale. I have found by lowering the TA, it allows for a higher pH (which is much more stable) while maintaining perfectly acceptable CSI levels.

In fact it's pretty easy to calculate a CSI that is well within the safe and acceptable range with a pH well into the 8's. So the question is what is the problem with a high pH, if the CSI is still at or even slightly below zero? Scale isn't going to form with negative CSI, so is it swimmer comfort that it needs to be in the 7s or is there something else?

 

[AUSpool]

An interesting question and I'm following along for sure.

My target pH has always been 7.6 but my pool likes to settle at 7.8, if I adjust it to 7.6 it goes right back to 7.8 so I've decided just to leave it at 7.8 and just monitor it. I have noticed an anomaly though, when adjusting my TA, after an addition of acid to bring my pH down to 7 it was back at 7.8 the next day. But with a second large acid addition to bring it down to 7 again it came up much slowly the second time.

My guess is that for most pools the pH rise will slow as it aproaches 8.3 which will give me a CSI of -0.12 if my other values are correct.

That doesn't come close to answering the question but I think it gets harder to manage the CSI the higher the pH gets.

 

[BattleOfYakima]

I believe these two threads will answer most, if not all, of your questions. Both are short and sweet. Please read and share your thoughts!
[h=1]Running SWG Pool with High (8.2) pH[/h][h=1]Is pH of 8.0 always a problem?[/h]

 

[pooldv]

Nice threads you found there Yak.

My pool is similar, pH constantly wants to rise, fill water is always pushing my TA up to 80-120 and everything here loves to scale, showers, coffee pots, etc. With properly managed CSI the risk of scale is eliminated. My pool and SWG cell are the only things around here with no scale. I see no issue at all with letting pH rise to 8.0 (and hopefully stop) and when it hits 8.2 then lower it to 7.8. Taylor makes a pH comparator block that reads to 8.2. Keeping CSI between -0.3 and 0 is the key. I would shy away from 8.2 and would not go higher because of eye irritation and inability to measure it.

Another point is that the pH scale is logarithmic and the farther away you get from 7 the bigger the jump is. So, going from 8.0 to 8.2 is a much bigger jump than 7.4 to 7.6.

And for lurkers, there is no benefit in trying to keep pH at any number below 7.8. That just creates work to constantly lower pH which lowers TA which you then have to raise with baking soda. Then the higher TA will push your pH up. Repeat!

But, yes, there are pools out there with TA 80-120 and pH of 7.4 to 7.6 and it never moves. How? I have no idea but I've seen plenty of them. Bottom line is for the most Trouble Free Pool is to try to let your pH and TA find equilibrium where neither one requires much effort to adjust.

 

[JoyfulNoise]

Me thinks you are putting too much faith in Pool Math....

I would not trust the CSI calculations when you have extreme conditions like yours - high pH, low TA, borates present, salt. The calculator relies on some tricky math and has in it some assumptions related to the range of pH in the water. The CSI calculator will not work for all pH/TA/Borate/Salt combinations. All you have to do to prove this to yourself is put some numbers in it - try 80ppm CYA, TA 50ppm, pH 7.8 to 8.4, Borates 50ppm, salt at 3600ppm. You can easily make the CSI go MORE NEGATIVE with increasing pH..... Then, at a certain point, the CSI field will return NaN which Java-speak for "Not a Number" (like a Divide-by-zero error).

The fact is, when the pH goes above 8.0, the solubility of calcium carbonate plummets. Scaling is a very real problem when pH goes that high and while it might not show up in your SWG cell, you can easily start to scale calcium out in your heater (if it happens to fire up) or on your tiling. You can certainly test it out and see how it goes, but I would not recommend keeping your pH above 8.0.

 

[BattleOfYakima]

both pooldv and joyfulnoise! Very helpful posts to help pool school graduates make educated choices. So is it fair to say the take away here is - 7.8 safe and you can place far greater faith in poolmath than if you leave 7.2-7.8. No one new to TFP or pools in general should allow 8.0s for long and it is indeed worth it, both short and long term, to get back to 7.8 frequently. If you know your water, fill water, chemistry trends in different seasons, and could teach a class on CSI, then you may experiment with 8 and 8.2, but you do so knowing that both your actual PH level and CSI calculations are now best guesses and no longer science? Something like that?

 

[pooldv]

7.8 is definitely safe. If you want to play it safe then lower pH to 7.8 when it reaches 8.0.

My pool is a constant scale test bed. Not by choice. My biggest problem is TA creeping up to 80-100 from the fill water. Life is good when TA is 50-60. And I need to place an order with Duda, I'm behind schedule on that. About a month ago I had pH at 8.0, TA 80, CH 400, borates 0, cya 80, salt 3100, CSI at +0.28. I took the solar cover off and there were scale flakes all over the sun shelf from the SWG. That is one handy thing about the SWG is that it will scale before the pool so it can be the canary in the coal mine.

 

[Texas Splash]

Well, this is a sore subject for me. Not because of TFP or the calculator, but because of my own ignorance "before" TFP. Even the 1st year after finding TFP, I was so thrilled to not have algae anymore I never tracked my CSI like I should. I kept a few testing notes back then only to realize later my CSI averaged around 0.7 - 1.1. My shell began looking lighter & lighter. Still nice, but I could see a difference. Even after lowering my CSI quite dramatically for several month months, the tarnished formation of scale all over the shell was set-in and too much for me to bear.

This Memorial Day weekend, I made a commitment to put a dent in that scale and started manual sanding. Yep. Try that in an 18K pool at age 53. Muscles and lungs are hating me, but I'm making progress. My floor is covered each morning with powdered scale like baby powder. I'm keeping notes of my tools & techniques, and taking photos of my progress to which I will post a new thread, hopefully near the end of this season where I describe for other FB owners my personal experience with the scale beast.

Now, where's the Tylenol?

 

[pooldv]

Good luck with that project!

 

[JoyfulNoise]

Well, this is a sore subject for me. Not because of TFP or the calculator, but because of my own ignorance "before" TFP. Even the 1st year after finding TFP, I was so thrilled to not have algae anymore I never tracked my CSI like I should. I kept a few testing notes back then only to realize later my CSI averaged around 0.7 - 1.1. My shell began looking lighter & lighter. Still nice, but I could see a difference. Even after lowering my CSI quite dramatically for several month months, the tarnished formation of scale all over the shell was set-in and too much for me to bear.

This Memorial Day weekend, I made a commitment to put a dent in that scale and started manual sanding. Yep. Try that in an 18K pool at age 53. Muscles and lungs are hating me, but I'm making progress. My floor is covered each morning with powdered scale like baby powder. I'm keeping notes of my tools & techniques, and taking photos of my progress to which I will post a new thread, hopefully near the end of this season where I describe for other FB owners my personal experience with the scale beast.

Now, where's the Tylenol?

Why not just do a zero-alkalinity treatment then dump half the water and refill?

 

[chiefwej]

After all the background reading, I can see that running any pH outside the accepted "norms" is not for the faint at heart and is certainly not something we would recommend on the forum.
But I have found that for my pool a pH of 7.8-8.0 is where the pool is the happiest. Trying to maintain anything below 7.8 is just frustrating. So I only add MA if the pH actually exceeds 8.0, and then only target 7.7, always keeping an eye on my CSI. I was not aware, until now that the CSI calculations from PoolMath were not always reliable and accurate. I'm hoping that if I keep out of the 8's with the pH, the CSI calculations will be close enough to keep me out of trouble.

 

[Texas Splash]

Why not just do a zero-alkalinity treatment then dump half the water and refill?

Well Matt, after all the discussion and what seemed like "unknowns" about effects on the gelcoat, I elected to not do that. Not that I didn't think about it, but I just wasn't sure about any possible ill effects. PS ~ Sorry Chief ~ didn't mean to hijack.

 

[JoyfulNoise]

Well Matt, after all the discussion and what seemed like "unknowns" about effects on the gelcoat, I elected to not do that. Not that I didn't think about it, but I just wasn't sure about any possible ill effects. PS ~ Sorry Chief ~ didn't mean to hijack.

I'd still do it. I would not want to sand a pool that large and your sanding is just going to make the surface roughness worse. A chemical treatment could reduce the haze more evenly.

But, it ain't my pool so.....Tylenol and Motrin can be taken in intervals. Full dose Tylenol, wait a few hours, then full dose Motrin. You'll feel great (but your liver and kidneys will hate you for it )

 

[chiefwej]

When I started on TFP I had a layer of scale on the pool surfaces. Just kept my CSI on the low side for several months and it very slowly went away.

Going back to my topic, another down side of running high pH is I have to occasionally go through the process of lowering the TA. My fill water is high CH and high TA. So, I can keep lowering TA, but eventually the high CH will get me, then no choice but to drain and start over. What the new water will look like is anyones guess. The CH level sometimes varies depending on which well the town is drawing from. Good news is the water is cheap. The salt, boric acid, and cyanuric acid costs a lot more than the water.

 

[brauh01]

Now, where's the Tylenol?


Well, at least I can help on one point! You want Motrin and not Tylenol. My assumption is you're taking for sore muscles and not some sort of headache.