Residue on new plaster

[ndakotaninja]

I got my pool re-plastered last April with a dark blue. We had some issues with it after the replaster, namely discolorations/staining, as well as both CH and pH rising consistently over the summer. I was going through about a gallon of acid a week to keep the pH in check. I also asked about the rising CH, as it should have stopped after a few months when it cured (Calcium levels in replaster), but didn't get anywhere.

Before winter, I balanced things one last time, drained it down, and closed it as usual. When I opened up the spa, everything that was flat below the water line (floor and benches), as well as the slopes transitioning the walls to the bench/floor, has a white/yellow residue on it, possibly scaling. I scrubbed it like crazy and managed to get it partially off some of the bench sections, but the slopes/tiles are extra hard to brush it off. Maybe someone can confirm that's what it is based on the pictures. One is

I didn't test the water until after I had already drained water out to put in the hand rail and filled it back up (so about half the water is new). The CH reading now says 325, so I can only assume it was higher over the winter and this is in fact scaling. So the question is, if this is scaling, what's the best way to clean it? I haven't taken the cover off the pool yet, but i can only assume it's going to be in the same situation, and it's going to be a lot harder to brush the bottom of if it's the same.

Thanks in advance.

 

[YippeeSkippy]

Got test results from last fall's closing as well as today?

Maddie

 

[ndakotaninja]

The readings for the pool before i drained it were:

ph- 7.8
fc - 7
cc - 0
CH - 500
TA - 50

Reviewed my notes, i was draining it about every 3 weeks below the skimmer line to drop the CH. pH i was going through about a gallon every week or 2. I opened the pool today and fortunately it's not as bad as it could have been. Doesn't look like there's calcium scale, but there is a TON of sediment everywhere (reminds me of the plaster dust when we first replastered last year). The walls/steps/floor about 1" under the water line are all slightly stained yellowish. I did a reading on the pool water and i'm filling it back up now:

FC - 0
pH - 8.6+ (almost purple)
CH - 500
TA - 160 (not sure how this got so high)

 

[blakeusa]

I would just fill the pool and drop the PH to 7.2 and just run it. At the lower PH I would expect after a couple of weeks and some brushing it should clear up.

 

[YippeeSkippy]

You've read this, right?? - Pool School - Calcium Scaling

Other than what is suggested, I don't know what else to suggest?

Maddie

 

[ndakotaninja]

Yes, I was wondering if anyone had any luck removing scaling without an acid wash or damaging their finish in the process by grinding it down. I've contacted the guy who redid it, and since the spa is the only thing with scaling, we could easily drain it and refill it if needed, so hopefully he can do something about it. But considering how bad he is at his job (hindsight's 20/20), I doubt he'll help.

The pool sediment is clearing up, but there is a noticeable discoloration on the walls for about 4" where the water line was over the winter. I'm hoping with brushing that will clear up this summer. Oddly I've put 3 gallons of acid in over the last 2 days and the pH is still too high to get a reading. Considering last summer the pH was rising with no explanation and i was going through a gallon a week to keep it in check, I'm really hoping that doesn't happen again this year, cause that gets expensive and time consuming.

 

[YippeeSkippy]

Are you using strips to test the pH or one of the block comparison testers?

Which test kit do you have??

Maddie

 

[blakeusa]

I have buffed/ wet sanded a couple of spa's and one 32k pool that had extreme scale. It was like 60 grit sand paper and acid would not touch it or knock it down.

All turned out perfect when done. Used disc sanders with 220 grit wet dry paper.

Acid washed after sanding.

 

[ndakotaninja]

Are you using strips to test the pH or one of the block comparison testers?

Which test kit do you have??

Maddie

It's the TF-100 test kit. It has the Taylor K-1000 blue box for the pH/chlorine tests.

I still haven't heard back from the builder, so i'll probably have to do sanding on the spa to clear the scale. The pool residue cleared up most of the way after several days of the filter running. It took 5 gallons of acid to lower the reading back into the 7.4 range. That acid addition also lowered the TA back into the 50s range where it was when i closed the pool.

So right now, everything is balanced, only remaining issue is the scale on the hot tub and a reddish stain about of 8 inches where the water line was over the winter. it goes around the entirety of the pool and now that the water isn't cloudy, it's pretty noticeable. I'm hoping that discoloration will go away with brushing over the summer.