What I believe to be scaling, requesting assistance with resolution

[tdi_jim]

Hi All,

We did a pool renovation last summer (August 2014), I closed the Pool on 9/20/14 with a PH of 7.2. The pool was opened yesterday and after opening yesterday and running the pump for 5 hours:




I am currently using CL tabs and once this is resolved I will add the salt and convert over to the SWG.

On the walls of the pool I have deposits with a texture similar to sand, I was able to brush these off and vacuum them out, see pic



If this is scaling did the minerals come out of the finish or the water?

Will keeping the PH at 7.5 during the season help dissolve whatever scaling might be there?


The deposits in the SPA are firmly attached and will not brush off, could the issue in the SPA be more serious due to the lower volume of water or difference in temperature over the winter?

What is the best way to remedy the SPA; I have read that an Acid wash or the use of a Pumice stone could make the surface smoother. I am leaning towards a Pumice stone, the spa is small and shouldn't take too long. Is the Stanley Pool Tec stone recommended?

Amazon.com : Stanley 36897 Pumice Stone - Large : Swimming Pool Cleaning Tools : Patio, Lawn Garden


Thanks,
Jim

 

[Azgirl71]

Someone else had this happen, but I cannot remember what they determined it was. Hopefully someone will remember.

 

[pooldv]

I believe it was determined to be pollen or tree debris in both of the two cases I remember. But, this looks a little more crystallized and less organic.

 

[Azgirl71]

There were 2 threads that had this crystallization.

- - - Updated - - -

Here is one of them.

Sediment/Crystals on pool bottom

 

[duraleigh]

With a pH of 9.0+ (how did you measure that?) and a CH of 350 ppm, that would certainly indicate calcium scale that came out of the water.....it did not leech out of the finish.

7.5 pH will probably prevent further scaling but won't get rid of what you have.

I have no experience on a particular brand but I would suggest a pumice stone on the spa as well.

 

[Patrick_B]

Welcome to TFP Jim,

Looks like the pH 9 was a pool shop reading? That would be considered extremely high for a pool if correct, but would certainly help contribute to minerals precipitating like that, even if it were a little lower.

What else have you used in the past? Specifically for pH control? I do suggest getting a proper kit to measure these things yourself and eliminate any doubt about your actual levels. Often, these store readings are wildly off from reality, but something is obviously going on here.

 

[tdi_jim]

Welcome to TFP Jim,

Looks like the pH 9 was a pool shop reading? That would be considered extremely high for a pool if correct, but would certainly help contribute to minerals precipitating like that, even if it were a little lower.

What else have you used in the past? Specifically for pH control? I do suggest getting a proper kit to measure these things yourself and eliminate any doubt about your actual levels. Often, these store readings are wildly off from reality, but something is obviously going on here.

Hi All and thanks for the replies. Sorry for the 9+ reading it was just a notation to myself to indicate what appeared to be an off the scale reading (above 8.2). I use the TF-100 test kit for my testing and the pool calculator to adjust chemistry. The 150oz of MA did bring the PH down to 7.5, I guess I could try to reverse calculate what effect 150oz of MA would have on ~35K gallons.

The history here is that it was renovated last August and the pool did have a very healthy appetite for MA. I was checking every 2 days and adjusting as necessary. I was using the TF-100 kit and the Pool Calculator and the two worked wonderfully.



I was a bit worried that I would not be able to control PH after closing. The Pool Contractor suggested I get the PH down to 7.2 and a TA of 120 prior to close which I did. When we opened it was as I described above. The surface of the finish looked to have crystals/sand on it which brushed off and vacuumed out. The surface feels a bit rougher than last season. I don't mind using pumice on the seating surfaces, but how best to handle the rest of the pool, is an acid wash necessary?

 

[Azgirl71]

Did you see my link in post 4?

 

[tdi_jim]

Did you see my link in post 4?

Yes sorry I forgot to mention that. I took a look at that link and my deposits not as crystalline as those in that thread and definitely not as severe as those calcium sulfate deposits mentioned in the article.

 

[Azgirl71]

Ok. Glad you saw it.

 

[umpalumpajay]

aaaaah, the mystery crystals!

 

[tdi_jim]

Update:

Based upon browsing this forum:

I tried dropping the sediment into MA and it fizzes, is this the acid test for calcium-something?

I believe that this is a minor scaling issue so I dropped the PH to 7.2 yesterday and it appears that vigorus brushing helps to remove what is left of the stuff.

I ordered some of the Stanley Pumice and will use it to smooth the seating areas. From day 1 the diamond brite was rougher than the plain marble dust plaster that was the original finish.

 

[chem geek]

Yes, you have confirmed that this is likely to be calcium carbonate scale. The acid is reacting with the carbonate to produce carbon dioxide gas.

The scaling was likely brought on by the very high pH, along with CH and TA that may have been "normal" (but not low).

 

[tdi_jim]

Thanks chem geek. I am going to be adjusting chemistry (TA) for a SWG, when I close this autumn (Oct - May). Is there anything you can recommend to avoid this happening next year? Lower CH? Testing and adjusting Chemistry while pool is closed?

 

[chem geek]

Because the pH ended up higher than would occur from carbon dioxide outgassing at your TA level (i.e. it was well above 8.4 in pH), the pH rise is most likely from the plaster since you had a renovation. The continued curing of plaster raises pH significantly. There is nothing you can do to stop it except to have done a bicarbonate startup when the plaster was done since that creates a more solid stable plaster surface with more complete and rapid conversion of calcium hydroxide (that would otherwise raise pH) into solid calcium carbonate as part of the plaster itself.

You could test and add acid when the pool is closed, but would have to do something to mix the water to prevent acid pooling. You could, as you suggest, lower your CH level, but then that risks some dissolving of the plaster over the winter though at colder temperatures that is much slower to occur and you'd have to add back the CH upon opening so that doesn't sound like a very good plan. You probably won't have this happen next year, or at least not as much, because the plaster should not be causing as much of a rise in pH by then.

 

[tdi_jim]

Thanks again, That makes sense the acid demand is lower than it was last year.

 

[gtemkin]

I put your numbers into pool math and the amount of acid addition didn't seem to correspond to the results you got. Would have expected an effect on TA but there wasn't any in your test results. I assumed 31.45% muriatic but you may have used the 14.5% stuff. The starting pH wasn't a firm number either so that could explain it. Your pool volume of 35000 seems pretty high for what looks to me to be a mid 20K pool. Can't say I can judge with certainty from the photo, but you may want to verify your volume calculations so you can hit your targets on the money in the future.

 

[tdi_jim]

I put your numbers into pool math and the amount of acid addition didn't seem to correspond to the results you got. Would have expected an effect on TA but there wasn't any in your test results. I assumed 31.45% muriatic but you may have used the 14.5% stuff. The starting pH wasn't a firm number either so that could explain it. Your pool volume of 35000 seems pretty high for what looks to me to be a mid 20K pool. Can't say I can judge with certainty from the photo, but you may want to verify your volume calculations so you can hit your targets on the money in the future.

Thanks, the first PH number was a guess since it was off the charts. The pool is 35K gallons, the length is over 50 feet, I took a water meter reading before and after filling it; the deep end is real deep at 9 feet.

For the first acid adjustment I will come clean and admit that I used 1 gallon of the 31.45% stuff and about 1/3 gallon of the mystery "safer no smell unknown percentage" MA that I had left over. I won't be buying that in the future. The home depot used to sell both types but now only carries the Safer stuff, I now buy the real MA at the masonry supply.

 

[chem geek]

When plaster is curing and releasing calcium hydroxide into a pool, the pH, CH and TA all go up. When one adds acid, the pH and TA are brought back down. So there is no net drop in TA if the acid addition is required due to plaster releasing calcium hydroxide.

The net drop in TA from acid addition only occurs when the reason for having to add acid (i.e. the reason the pH is rising) is from carbon dioxide outgassing.