Unexplained pH rise

[AUSpool]

Just for the record I run my pH and TA a little higher in winter to offset the CSI affect of cold water. Keep my CyA a little lower (50ppm) through winter also.

I have a little gizmo that doses the LC slowly, I can walk away and do other weekly pool maintenance chores. So I'd be out there either way, the manual LC dosing chore is not actually additional time, and very little extra effort.

Do you have a photo of this gizmo? Do you think it could be adapted for acid delivery?

 

[needsajet]

SWGs here in Sydney run all year (colder water than yours). USA models shut off at certain low temperatures, TBMK around 10 degrees C. Our water barely gets that cold, so I have no idea if our SWGs shut off, but they certainly show low salt indicator lights, their internal sense of current between the plates, which is lower in cold water. The clouds of gas coming off the plates that we can see through the clear housing continues, though does seem to me to be a bit less swirling clouds when water is cold.

As to winter pH, there's an amazing plaster expert poster here by the name 'onbalance'. He's mentioned his view that pH checking and acid additions could be suspended for pools that are "open" but cold, without bothering plaster. I stop adding acid in winter, but do monitor pH. I can't say I never, ever get scale on the SWCG plates, but it's not often.

 

[Newdude]

During the day, each day:
4 hours no-SWG for ~3 months of winter
4 hours SWG for Spring months
4 hours SWG for Fall months
8 hours SWG for Summer months (swim season)*

So double the aeration in the summer for the SWG.

But I also allow my pH to rise a bit in the winter (7.8-8.0), to counter the effects the low water temp has on my CSI

So you let it be where it wants to be for the winter and it rises less.

There is an ongoing debate about the affects of an SWG on pH. I think I'm in the "it does" camp.

But then you point a finger at the SWG

Yes you see more PH rise with the SWG, but it's the pump and/or you preferring a lower ph IMO

 

[Dirk]

So double the aeration in the summer for the SWG.

I know of this aspect of the debate. It seems logical, and it stands to reason that it must account for some of the rise, it just doesn't track (to me) that it accounts for all of it. And you took a bit of a leap there, because I didn't explain fully. When I switch from four hours to eight hours, I also adjust the output level (lower). So the plates aren't producing bubbles twice as much. More, yes, to account for the greater FC loss in summer heat, but not double.

So you let it be where it wants to be for the winter and it rises less.

Not quite. I'm still adding acid all winter, as I am monitoring (testing) and dosing as needed. I just alter the target from ~7.6 to ~7.9. I know, from experience, that forcing pH down to 7.6 takes exponentially more acid than pushing it down to 7.9. The 7.6 and 7.9 targets are determined by my Pool Math CSI calculator. The winter and summer water temps determine the pH target necessary to maintain my target CSI (-0.3 to 0.0). And to be more accurate, it's not binary, it's actually a sliding scale. Fall and Spring have their own water temps and respective pH targets. I use the CSI calculator all year long, and adjust the pH target all year long.

My pH is a constantly moving target. It's just math (Pool Math math). The water temp is a constantly changing variable, but outside of my control. The CSI target is fixed (so not a variable, but just as much out of my control). So I move my pH target (the only thing I can control) to account for the water temp, to keep my CSI constantly in range.

And for others trying to follow along, this would be considered overkill. Some here merely advise (paraphrasing) "ignore CSI and keep your pH in the 7s." I don't have any direct evidence one MO is better than the other. But I do have some anecdotal evidence. What I'm doing with pH is very easy to do, and I'm a big believer in maintaining CSI in range, due to the total destruction of my plaster by a pool company that completely ignored CSI. So I am no doubt overcompensating, but as I said, it doesn't require any extra effort on my part to do so.

But then you point a finger at the SWG

Yes you see more PH rise with the SWG, but it's the pump and/or you preferring a lower ph IMO

I see what you're getting at. Keep in mind some of my posts might have been written by an intern, so you'll have a tough time proving in court it was me! But seriously, I agree, my 7.6 is absolutely costing me acid. I'm just not 100% that my SWG is not also costing me some.

When I first came on board here, "SWGs cause pH rise" was a thing. I believe I saw that in my pool when I first had one installed. And that was before I was tweaking my pH as I do now. That's really all I'm going by. This was before I understood anything, and didn't know how to track chemical dosing and its effects. It just stuck in my head. But I framed this theory carefully, you'll notice, with escape hatches like "there's a debate", "some people say", "I think I think this way or that way", etc. Plausible deniability!

The debate is interesting, but my overarching philosophy of pool chemistry has been the same for a while now: "My pool tells me what it wants me to do and I do it!" I don't ask "Why?" as much anymore, like I once did.

I like my pH to be close to 7.6 when I'm in the water. That happens to keep my CSI happy, so that works out fine. I don't mess with that.
I don't care what my pH is in the off-season, I just want my CSI to be happy, so I give my pool the little acid it asks for. In the grand scheme, it doesn't actually matter to me if my SWG is responsible for an increase in acid consumption, or if it is my 7.6, or both. I'm confident that what I'm doing is good for my plaster, or at least not bad for it. I'll let you know in 20 years if I was able to get my plaster to last 25 years, instead of the six years the first round of plaster made it. That's ultimately all I'm after, because whether an SWG causes pH to rise or not, the rise in the cost of a third plaster finish is going to be inevitable, and painful, if I can't get #2 to outlive me.

 

[Dirk]

Do you have a photo of this gizmo? Do you think it could be adapted for acid delivery?

It may not be what you're envisioning! But I do use if for both chlorine and acid, just rinsing in between. I originally built it for acid. It's no great invention of automation, it just frees up my hands and lungs to go do other things while slowly dosing a couple cups at a time. I have to refill it a few times for chlorine, not for acid. It's just a measuring cup with a hole in it suspended over the water. It was a solution to some trouble I had with using acid (spilling it, inhaling it, getting it on my hands and clothes, etc). Here, in a very long thread about my initial travails with Muriatic (and other newbie things). This link jumps to the posts about the gizmo:
#96

 

[mgtfp]

Our water barely gets that cold, so I have no idea if our SWGs shut off, but they certainly show low salt indicator lights, their internal sense of current between the plates, which is lower in cold water.

I don't think they so. My pool gets down to about 8°C in winter, no issue. Depending on salt level, higher outputs may not work and low salt shoes up, but that could even be compensated with higher salt levels, working range of Aussie models is usually huge. But no need really, who needs high outputs in winter.

I did the experiment once, out of curiosity. I put an amp meter into the circuit and cranked up the output. Current kept as expected linearly growing with the output setting. When I reached the highest setting, the current didn't increase further and the low salt light came on (i.e. current on setting 8 with low salt light on was the same as current on setting 7 without light on). Added a bag of salt, and then I was able to get to the highest output with the expected current flowing.

 

[Newdude]

And you took a bit of a leap there, because I didn't explain fully. When I switch from four hours to eight hours, I also adjust the output level (lower). So the plates aren't producing bubbles twice as much.

Not plate bubbles, pump runtime. 4 hours to 8 hours of the pump aerating the water is double.

know, from experience, that forcing pH down to 7.6 takes exponentially more acid than pushing it down to 7.9.

And also from experience (as you experience in the winter) that it bounces back quicker from the lower ph than it did at the slightly higher ph.

I'm just not 100% that my SWG is not also costing me some.

I certainly can't say the SWG has zero effect, but the other two factors take most the blame here. The other typical SWG/PH beef when non TFP-ers switch is due to them no longer using pucks in addition to the pump runtime increasing by many hours a day. Again, it appears it's the SWGs fault when at least a good portion of the blame lies elsewhere.

That's ultimately all I'm after, because whether an SWG causes pH to rise or not, the rise in the cost of a third plaster finish is going to be inevitable, and painful, if I can't get #2 to outlive me

I totally get the micromanaging. And best wishes.

 

[Dirk]

I'm with ya on all points.