CH Increasing + White Spots on Plaster

onBalance said:

The few white spots in your photos are NOT the same as what I wrote about in my article "White Spotting." Nor are they "calcium nodules." They are a minor plastering defect, which means they are not caused by unbalanced pool water, whether it be aggressive water or scale forming water. If there are only a few spots like that, then I won't worry much about them. Just unfortunate that they occurred and are there. And I doubt that those few spots would be the cause of the notable calcium increase.

You have grasped and understood the information provided to you very well.

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Thanks for the info! That does make me feel much better!

There are only a few little spots like that. I see 6-8 total, plus maybe some really tiny ones I can see from the pool deck that could be either a “spot” or just a larger chunk of white aggregate. Visually, they’re really not very noticeable, and if they’re a plastering defect, then I guess it’s possible they’ve been there all along and I just never noticed. I admit, I’m looking much more closely at the plaster job now that I probably ever have.

In addition to the small, very bright white spots, there are a couple others that are more mottled looking and do bug me visually because they are larger. The two in the photo are about 1” in diameter. The one toward the bottom of the pic is definitely a depression in the plaster, and the other one feels the same as the surrounding surface. Do these appear to be defects and/or normal color variations/mottling?

I am still completely at a loss to explain the high CH levels. I really don’t think my fill water is the culprit. Even before now, I had measured the CH of the fill water from time to time, and it was always soft. And in the past couple days, I’ve measured it at various times of the day and after varying water demand from the house, and it’s always CH 0.

The only thing I can possibly think of is that some limestone dust from the coping is falling into the pool and dissolving, but I’m not even totally sure whether any of the coping is limestone. The orangey rocks could be, but I don’t know for sure.

I will do a partial drain & refill. Is a CH target of 800 reasonable? That would be about 1/3 of the water being exchanged and assumes no softened water being added to the pool.

I decided to do a little science experiment. I swept up some of the dust and grit from the stone coping and added a bit of muriatic acid. It bubbled. I’m not sure that my experiment is conclusive, but I take it to mean that it’s likely there is at least some limestone dust in the stuff that gathers near the pool.

So maybe it is the dust that’s contributing to my high CH? Does that seem like a reasonable possibility?

Thanks again!

It really does bug me that I can’t come up with an explanation for the increasing CH. It’s coming from somewhere, but I’m totally at a loss as to explain where. Nothing that I add to the pool has any calcium, as far as I know, unless there’s some lurking in either my bleach or muriatic acid under the “other ingredients”, but I highly doubt that. Nothing else goes into the pool with any regularity, and I haven’t so much as used a single chlorinating puck, ever. I’m sure the rock “dust” is adding some calcium, but not enough to explain the sharp increase.

Anyway, the pool contractor got back to me today, which is good. I emailed a detailed account of everything that I’ve observed, so we’ll see what the response is. If the CH & spots are simply quirks of my pool, I can totally live with that, but at least now I’ve alerted the contractor and it’s documented just in case it is something that needs to be fixed.

I’m still waiting for a reply from the pool contractor, but in the meanwhile, I just can’t get over the idea that something is going on.

Just as a note, I did a 20% ish drain & refill a couple days ago, and my CH is 850. I also measured the CH of the fill water throughout the refill, and it remained soft until the very end, when I got a single measurement of 20ppm CH. So for sure, the softener is doing its job. I’ll probably repeat the partial drain before long, but I didn’t want to tax my well too much nor allow the plaster to dry out in the TX heat.

During the drain, I noticed a couple more of the very small, bright white plaster defects/spots on the pool stairs. There are at least 4 of these on the top step alone, and although they *could* have been there from the re-plaster, I really don’t think they were. Under water, it’s hard to distinguish the defects from white plaster aggregate, but it was more obvious when I drained some water. Also, when I scraped at one of the flat, “new” spots with my fingernail, some chalky white material popped off and revealed the small depression in the plaster underneath.

Also, I’m paying more attention to the mottled colors on my pool floor now. I’m quite sure some of the discoloration is new, although I had noticed the largest area last summer but chalked it up to no big deal because it was the only such mottled area I noticed at that time. However, now I’m seeing that the plaster is definitely a bit mottled throughout the pool floor. Again, it’s not terribly unsightly, and I realize plaster is never perfect. But taken together with the mystery of the rising CH, I just can’t shake the feeling that something is up. I found the areas to be quite difficult to photograph, but hopefully y’all can appreciate what I’m trying to highlight. I promise, the discoloration is more obvious in person.

Any thoughts? Am I making a big deal out of “normal” plaster discolorations or does this look like a potential problem?