What's This on My Plaster?

[HouTex]

In the last couple of weeks I've noticed some splotches on the bottom of my pool--mainly on some of the steps and in the shallow end. They could have been there longer or just not as noticable. Please see the attached photo. It's the lighter colored sort of round marks. They don't come off with a steel brush and they seem to be in the plaster itself. I know that it's common for Luna Quartz to have imperfections and perhaps that's all this is. The Luna Quartz is still young--about six months old. I'm still adding about a gallon of MA each week to keep the pH in the 7.5 range. The water is very clear and blue. Here are this morning's test results from my TF-100:

FC 4.5
CC 0.0
pH 7.2-7.5 (added 1/2 gallon of acid yesterday morning; it will be back up to 7.8-8.2 in a few days)
TA 90 (I'm trying to get it lower; it's hard with 200+ TA fill water and no rain)
CA 480 (two pool stores put it more like 300)
Salt 3600
CYA 60 (I know it needs to be closer to 80)
Borates 80

Any ideas as to what this could be?[attachment=0:3bulrxfw]Pool Pic 1.pdf[/attachment:3bulrxfw]

 

[poolgirl22]

I can't address the original question as I'm not familiar with that surface type. However, on first very quick glance as I'm walking out the door... part of the increases in Ph are related to the fountains. Fountains aerate the water. Aeration of water raises Ph.

Try shutting the fountains down and see if the ph holds longer.

I'm sure another member can address the picture/question.

 

[HouTex]

Thanks. We rarely run the fountains--maybe three times since the pool was finished in early December 2010 and only for a few minutes each time. I think the spillover spa, the 2 hp pump, the highish TA, and the SWG all contribute to the rising pH.

 

[HouTex]

Any ideas anyone?

 

[blakeusa]

Just looks like motting or changes in the plaster color. Is it smooth or raised. If smooth it;s just color change.

 

[HouTex]

It's smooth, just like the entire surface of the plaster.