Lighter, Brighter Shade of Blue Plaster at Deep End

[Michael1]

If I don't destroy my pool, and myself, it is going to be a miracle.

The plaster in this pool is blue in color, and somewhat mottled with age. There is an area at the deep end that is brighter blue than the rest of it. I think this may have happened when I added acid at one of the jets at the deep end. At the time, I did not know you were supposed to use a brush to move the acid around on the bottom of the pool. I did use a net to blend it in, but I don't recall how deep I went. This is also the time I got acid fumes in my eyes, so I was not thinking the best at that point. I didn't really notice it before, but I recently have been changing some of the water, and noticed it. Maybe it has something to do with the tap water coming in, also at the deep end (although the brighter area is at a right angle to the tap water flow).

The pH has been very high recently 8.2, and I have done water changes, because I just could not get everything balanced. cYA was 160, and CA was 750.

Was:

CYA 160
FC 7
CC 0
CA 750
TA 160
pH 8.2

My water is now:

CYA 70
FC 13.5
CC 0.5
CA 450
TA 130
pH 7.6

I don't know if I should lower the pH of the pool to see if the color will blend better. Let me know what you guys think.

 

[PAGirl]

The experts are going to want a full set of test results, I am guessing....

 

[Michael1]

Good point. I added the before water readings.

I'll upload a picture later. It appears that the rest of the pool has some sort of deposit on the surface that is making it look dingy compared to this bright spot of about 2 feet by 6 feet. I am wondering if I have iron or copper light staining.

 

[Michael1]

Since I have not gotten any response on this, I'll have to guess. I'm thinking that the rest of the pool may have a light layer of copper or iron that the acid removed when I poured it in without brushing it. The area where I believe the acid settled, actually looks really nice and clean. So the goal is to get the rest of the pool to look like that. I'm going to try some metal removers and see what happens.

 

[chem geek]

Ascorbic acid will remove iron stains most readily; citric acid will remove newer copper stains more readily; older copper stains may require more significant acid and etching to remove so may not be worth it.

 

[zea3]

I think you may have calcium carbonate scale on the plaster since before the water change your CH was 750, TA 160, and pH 8.2 (possibly higher). These are all indicators for possible scale formation. You still have high TA and high CH 450. To prevent more scale from forming you would lower the TA to 70ppm, and keep the pH in the 7.0-7.2 range. This will also reduce the existing scale over time, and regular brushing will help loosen it. Metal sequestrant, such as Jack's Magic #2 can also help to loosen and dissolve scale.

You can also use MA to treat calcium carbonate scale on plaster surfaces. You may want to test a small application of MA or dry acid on a stain in the shallow end of the pool to see if it removes the stain.

 

[Michael1]

I really appreciate the suggestions. Scale did cross my mind, but it threw me off when I couldn't feel any roughness, and didn't see any scale on the tiles. What you are saying makes sense, though, so I will give these suggestions a try.

If I can get the rest of the pool to look like the deep end, it's really going to pop.

Thank you!