I had a much faster pH rise when my plaster started to form volcanoes (calcium nodules), drips, and delaminate so yes a poor plaster job that starts to release calcium hydroxide from under the plaster will have the pH, TA and CH all rise.
Running pH 7.8-8.0 vs chasing the acid dragon.
- Thread starter lalittle
- Start date
My gears are turning here, wondering why the op is getting such a persistent pH rise with no SWCG and long since cured plaster.
Could it possibly be somewhere in the plumbing that there occurs a high rate of turbulent water due to a minor constriction, or a wacky elbow setup, or tee, or even a reducer causing some sort of cavitating? Thus inducing a pH rise like one would see with a water feature, or SWCG.
Maybe a suction side leak that's sucking in air, cuasing aeration?
A possibly silly question, even though the plaster is only 15yrs old, if there were some sort of breakdown occurring, could this cause a pH increase? I'm thinking no, but worth a shot.
Lastly, could some sort of "mystery chemical" still be present, in-spite of the partial drain and fills, causing pH to rise?
Just some ideas... puzzling indeed.
Sent from my PC36100 using Tapatalk 2
Tony,
It's funny -- you basically just hit on all the things I've been asking about and looking into for the past few years (you could probably find several of my threads talking about these very things if you searched the forums.) I changed all my valves, and even hired a leak specialist, but everything checked out okay. I STILL, however, can't help feeling like a suction side leak (and/or something causing cavitation) is at least partially (if not wholly) responsible for the problem. This has been my best guess for a long time, but I've never been able to prove it. I CAN see bubbles in the check valve before the pump, however, so air is getting in there somehow. After fighting with this for a few years, however, following up on all sorts of theories as to where the bubbles were coming from, I kind of just wore out. You're post makes me want to get back into investigating this.
Thanks for your feedback -- everything helps, including people simply theorizing about the situation.
Larry
That's an interesting reply. For the past several months I've started noticing little white bumps forming on the bottom of the pool in the shallow end. I just chalked it up to some form of scaling from before I was paying as close attention to the CSI, but it has always struck me that unlike the typical scaling I used to see on the tiles, these bumps seem to be MUCH harder, and they still seem to be forming even though I've been keeping my CSI balanced. How does one investigate this?
Thanks,
Larry
y_not
0
I would say to start with some good photos showing the area of concern.
Thanks for the acknowledgment, it's good to know I'm not entirely off base here.
Sometimes just a fresh set of eyes, a clear head that has had the opportunity to decompress and reset, and fresh new ideas can make all the difference in the world.
So do we want to turn this into a troubleshooting thread, or should I be quiet with my crazy ideas and go away? Lol
I have more crazy ideas if anyone is interested. I'm a very out of the box thinker.
BTW Chem Geek, COOL insight into the effects of degrading plaster.
Op, that would TOTALLY BITE if your plaster is having problems after only 5yrs. :thumbdown: No beuno!
Sent from my PC36100 using Tapatalk 2
Thanks for the acknowledgment, it's good to know I'm not entirely off base here.
Sometimes just a fresh set of eyes, a clear head that has had the opportunity to decompress and reset, and fresh new ideas can make all the difference in the world.
So do we want to turn this into a troubleshooting thread, or should I be quiet with my crazy ideas and go away? Lol
I have more crazy ideas if anyone is interested. I'm a very out of the box thinker.
BTW Chem Geek, COOL insight into the effects of degrading plaster.
Op, that would TOTALLY BITE if your plaster is having problems after only 5yrs. :thumbdown: No beuno!
Sent from my PC36100 using Tapatalk 2
Doing some quick math, I figure that my corrected TA is probably around 40 at the moment. In the scale above, that would mean that pH rise would stops at a pH of 8.05. The corrected TA I'd need to fully stop pH rise at a pH of 7.8, however, is 22 -- nearly half of what I'm seeing. Given this, the critical piece of information lies in the statement "outgassing slows down considerably before that point." Just how far below the "stopping" point do you still get substantial slowing in the pH rise, and how much slowing does "substantial" mean? I don't know if "considerably before" could include "22" in my example, and I don't have a feel for how much slower it would be at this point. Are we talking a slow down of 40%, or 95%, or...? I don't have a point of reference, and I can't drive the TA low enough to test it. Since I'm not sure if there is some other cause for the pH rise, I have no way of even guessing if my pH rise is due to outgassing or not.
Do you have any further information on this? If I had some idea of what to expect at a given pH and a given TA, I could take an educated guess as to whether something else is going on here.
Thanks again,
Larry
You can most readily distinguish pH rise from outgassing vs. from alkaline sources because when you add a strong acid to lower your pH, your TA will drop. With carbon dioxide outgassing there is no change in TA so you'll know if your pH rise is from carbon dioxide outgassing by seeing that the TA is dropping over time by the expected amount based on how much acid you are adding. That's the easiest way to tell. In your 22,000 gallon pool, one gallon of full-strength Muriatic Acid (31.45% Hydrochloric Acid) lowers the TA by 22.8 ppm.
The other way to tell would be to let the pH rise and see if it stops or significantly slows down as it approaches the equilibrium level for your carbonate alkalinity level. Of course, this is risky if you have metal ions in the water or if your pool is saturated with calcium carbonate since the rise in pH could stain or scale -- depends on how much the pH rises.
If your TA is already down to 40 or so and the carbonate alkalinity is below that, then unless you've got a lot of aeration in your pool I suspect the source of the pH rise may be due to something else though what exactly is a mystery. If the plaster were newer, it could be from that. For older plaster it would only cause a rise if it were degrading such as you seeing calcium nodules forming. You said you notice that (small white bumps) so I'll bet that is what is going on (unfortunately). As I noted, if you are adding acid and yet the TA doesn't seem to be dropping over time and especially if the CH is rising over time, then that is most likely calcium hydroxide from the plaster (behind the surface, coming through as calcium nodules).
As I noted in my earlier post, I had this happen in my own pool around year 7 and it's very unfortunate. It created higher pH rise for a couple of years and showed calcium nodules and drips and even delaminated in a couple of places. It seemed to stabilize around year 10 (last year) and things seem stable this year as well. Clearly with the delamination, they didn't do a good job with an even and well bonded (to the gunite) plastering (there is a clear void) so I suspect there were some areas that were thinner or weaker and they didn't to a bicarbonate startup so the plaster thickness may have been too thin in some places. Eventually over time some places broke through pinhole openings and the calcium hydroxide from behind the surface came out. Not good.
The other way to tell would be to let the pH rise and see if it stops or significantly slows down as it approaches the equilibrium level for your carbonate alkalinity level. Of course, this is risky if you have metal ions in the water or if your pool is saturated with calcium carbonate since the rise in pH could stain or scale -- depends on how much the pH rises.
If your TA is already down to 40 or so and the carbonate alkalinity is below that, then unless you've got a lot of aeration in your pool I suspect the source of the pH rise may be due to something else though what exactly is a mystery. If the plaster were newer, it could be from that. For older plaster it would only cause a rise if it were degrading such as you seeing calcium nodules forming. You said you notice that (small white bumps) so I'll bet that is what is going on (unfortunately). As I noted, if you are adding acid and yet the TA doesn't seem to be dropping over time and especially if the CH is rising over time, then that is most likely calcium hydroxide from the plaster (behind the surface, coming through as calcium nodules).
As I noted in my earlier post, I had this happen in my own pool around year 7 and it's very unfortunate. It created higher pH rise for a couple of years and showed calcium nodules and drips and even delaminated in a couple of places. It seemed to stabilize around year 10 (last year) and things seem stable this year as well. Clearly with the delamination, they didn't do a good job with an even and well bonded (to the gunite) plastering (there is a clear void) so I suspect there were some areas that were thinner or weaker and they didn't to a bicarbonate startup so the plaster thickness may have been too thin in some places. Eventually over time some places broke through pinhole openings and the calcium hydroxide from behind the surface came out. Not good.
Just to clarify, does this mean that pH rise caused by factors OTHER than outgassing will also cause a rise in TA? That seems to be a result of the above statement -- i.e. if the TA does not drop as fast as you'd expect from acid additions, it would follow that something is pushing the TA up a bit.
My TA is definitely dropping over time, but I'm not sure how fast -- I never tracked it accurately. On this note, doesn't TA rise over time from using liquid Chlorine? If so, this makes it difficult to determine how much effect any acid additions are having on the TA unless I also know how fast it's rising. I can't add an entire gallon of acid at once since this would push my pH WAY too low, so I need to do it over time. Since the TA rises over time by an unknown amount, however, I can't tell how much effect a given amount of acid is actually having.
If I had to guess, however, I'd say that a third of a gallon of acid (which brings my pH down by 0.4) knocks my TA down by perhaps 3 to 5 points. It's tough to tell due to the nature of the test, which is based on multiples of 10. Based on one gallon dropping TA by 22.8 points, I "should" be seeing a rise of 7.6. While I'd say that this isn't outside the realm of possibility, my guess is that my rise is lower than this. This, combined with the little white nodules, leads me to believe that some of my pH rise is based on an issue with the plaster.
If this is the case, just how "bad" is it? Can I run it this way as long as I keep an eye on the CSI, or is this a problem that requires specific attention? I contacted the previous owner to see who did the plaster, and unfortunately, he couldn't remember who did it, so I can't rely on any sort of warranty, let alone even tell what any warranty might have been offered.
What's the recommended course of action here?
Thanks again,
Larry
Yes, pH rise caused by factors other than carbon dioxide outgassing will also cause a rise in TA.
Any TA rise from using chlorinating liquid or bleach is also associated with pH rise and both are due to the small amount of "excess lye" which raises both pH and TA, but unless you are using very poor quality product, this is a small effect. For high quality 12.5% chlorinating liquid, it would take 100 ppm FC cumulatively added to raise the TA by only 2.4 ppm.
Also, don't forget that TA will rise from evaporation and refill since the TA (and CH) from the fill water will be added to the pool.
As for what to do, yes you can just keep operating as usual but having the higher acid demand until things settle down. That's what I did in my pool.
Any TA rise from using chlorinating liquid or bleach is also associated with pH rise and both are due to the small amount of "excess lye" which raises both pH and TA, but unless you are using very poor quality product, this is a small effect. For high quality 12.5% chlorinating liquid, it would take 100 ppm FC cumulatively added to raise the TA by only 2.4 ppm.
Also, don't forget that TA will rise from evaporation and refill since the TA (and CH) from the fill water will be added to the pool.
As for what to do, yes you can just keep operating as usual but having the higher acid demand until things settle down. That's what I did in my pool.
Okay -- so the presence of some nodules is not a sign that something much worse is about to happen (based on the fact that they're caused by voids due to small holes or cracks.) When this happened to you before, you didn't have to do anything dramatic, did you? What actions did you take?
I normally use Hasa Chlorine, but sometimes I use Leslie's if I need it quick and the other stores are already closed (Leslie's stays open later.) In a real pinch, I sometimes use Home Depot, but not all that often. The Leslie's and Home Depot are both 10%, but the Hasa is 12.5%. I would assume that Hasa is a decent quality product, but that the other two are questionable. That said, I really don't notice a difference in TA rise using one vs another, and I've seen "bad" batches of Hasa Cl before, where it was noticeably weak for some reason (the Cl rose by only a fraction of what it should have.)
Thanks,
L
I normally use Hasa Chlorine, but sometimes I use Leslie's if I need it quick and the other stores are already closed (Leslie's stays open later.) In a real pinch, I sometimes use Home Depot, but not all that often. The Leslie's and Home Depot are both 10%, but the Hasa is 12.5%. I would assume that Hasa is a decent quality product, but that the other two are questionable. That said, I really don't notice a difference in TA rise using one vs another, and I've seen "bad" batches of Hasa Cl before, where it was noticeably weak for some reason (the Cl rose by only a fraction of what it should have.)
Thanks,
L
I took no actions, other than being ****** off that my contractor apparently used subs who rushed or otherwise didn't do a great plaster job. I just added acid to keep the pH in check. It wouldn't slow down as the pH rose. If I didn't add acid, it would have kept climbing higher and higher.
I use Hasa and it presumably does not have a lot of excess lye in it. Hasa told me that they have a 0.2% excess lye and a pH of 12.78. I think their calculation did not account for ionic strength so the pH may be less, but in any event it's not a lot of excess lye.
I use Hasa and it presumably does not have a lot of excess lye in it. Hasa told me that they have a 0.2% excess lye and a pH of 12.78. I think their calculation did not account for ionic strength so the pH may be less, but in any event it's not a lot of excess lye.
So it was about 10 years before it stopped? Wow -- that's disheartening. Mine's been doing this (mysterious pH rise) for 4 years now, but the spots only appeared a year or so ago (maybe a bit more). It sounds like your rise didn't start until the nodules appeared, but in my case, the rise was happening WELL before any visible signs of calcium nodules started. How did you deal with the spots that delaminated? Don't you need to patch those? For the nodules, did you sand them down?
L
L
No, the problem only started at year 7 and it pretty much stopped 3 years later (last year). My more rapid pH rise was only noticeable once the calcium nodules and drips appeared. Prior to that I had minimal pH rise, though I still had some which was unusual given I had a pool cover on most of the time. The amount of acid needed roughly doubled starting in year 7 but at year 10 went back to normal.
The delaminations are still there. One is between the shallow and deep end so not normally stepped on while a much smaller one is in the shallow end. We're just living with this for as long as we can until we need to replaster, perhaps in a few years which would put us closer to the 15 year "expected" life though one should be able to do better with a good plaster job. I only sand down the nodules in areas where we walk. I don't bother doing anything with the drips and nodules in the deep end.
The delaminations are still there. One is between the shallow and deep end so not normally stepped on while a much smaller one is in the shallow end. We're just living with this for as long as we can until we need to replaster, perhaps in a few years which would put us closer to the 15 year "expected" life though one should be able to do better with a good plaster job. I only sand down the nodules in areas where we walk. I don't bother doing anything with the drips and nodules in the deep end.
I'll count myself lucky that no delamination has occurred. My pH rise has been there from the get go, which was probably about a year to a year and a half after the plaster was re-done.
My impression is that my pH rise does slow a bit as the pH goes up. I can't be certain about this, but after living with it for a while, my gut feeling is that this is the case. Would this still be consistent with the presence of the calcium nodules, or does this imply that I also have some rise due to outgassing.
Just out of curiosity, how long after your nodules started appearing did the delamination occur? Was it right away, or did you have the nodules for a while first? Also, how long was it before the nodules reached their "peak," and no new ones occurred? I'm curious if there's any way to estimate how far into the process I am, and if the issue will continue to get worse. I know it's impossible to know anything for sure, but I'm wondering if it's possible to make an educated guess based on the other people's experience and the specifics of what I'm observing.
Thanks again for all the feedback here, which really helps.
Larry
My impression is that my pH rise does slow a bit as the pH goes up. I can't be certain about this, but after living with it for a while, my gut feeling is that this is the case. Would this still be consistent with the presence of the calcium nodules, or does this imply that I also have some rise due to outgassing.
Just out of curiosity, how long after your nodules started appearing did the delamination occur? Was it right away, or did you have the nodules for a while first? Also, how long was it before the nodules reached their "peak," and no new ones occurred? I'm curious if there's any way to estimate how far into the process I am, and if the issue will continue to get worse. I know it's impossible to know anything for sure, but I'm wondering if it's possible to make an educated guess based on the other people's experience and the specifics of what I'm observing.
Thanks again for all the feedback here, which really helps.
Larry
You probably have both -- that is, some pH rise from outgassing in addition to the calcium hydroxide.
The delamination occurred about 2 years after the first nodules, but I don't think they are necessarily connected unless there was some shifting of the pool substrate (settling of the soil?) that perhaps caused stresses to the pool plaster that triggered some of the effects. One would expect the gunite shell with it's rebar to be very solid, but at least for the shallow-to-deep transition I can imagine any settling stresses to be greatest there.
I wouldn't take my single experience as predictive of yours. If someone like onBalance or some pool builders or service personnel have seen this over multiple pools, then that would give a better idea for prediction.
The delamination occurred about 2 years after the first nodules, but I don't think they are necessarily connected unless there was some shifting of the pool substrate (settling of the soil?) that perhaps caused stresses to the pool plaster that triggered some of the effects. One would expect the gunite shell with it's rebar to be very solid, but at least for the shallow-to-deep transition I can imagine any settling stresses to be greatest there.
I wouldn't take my single experience as predictive of yours. If someone like onBalance or some pool builders or service personnel have seen this over multiple pools, then that would give a better idea for prediction.