Streaks / light patches in plaster

[Dparnell]

My pool has been complete and running since January. The pebble finish was very consistent throughout the entire pool. Lately I've noticed some lighter areas and some lighter streaks developing in the plaster. I test the water weekly and follow the advice and target numbers in pool school. What could be causing the inconsistent colors? Could my low CH level be causing it?

test results from this morning.
CH 250
TA 100
CYA 90
CL 7
PH 7.8 (I added some acid to bring it down to 7.5)

I tried to take a couple pictures but you couldn't notice the color changes in the pics.

thanks

 

[Texas Splash]

Well, your minimum CH for a SWG plaster pool is 350. I wasn't able to calculate your CSI since your pool gallon size isn't listed in your sig, but you might want to check. What you're describing seems like it could be related to that low CH. Since your pool so new, it may be worth notifying the builder right away as I would assume it's still under warranty. Perhaps they will have some explanation related to the curing process they did that may help explain.

 

[Dparnell]

Thanks Pat. Pool is approximately 27,000 gallons.

 

[Texas Splash]

I entered your info into the calculator and it showed a CSI of -0.22 (w/ pH at 7.5) and 0.06 (w/ pH at 7.8)

Calcite Saturation Index - requires pH, TA, CH, CYA, Temp, uses Borate, Salt
Less than -0.6 is suggestive of problems for plaster, tile, stone, and pebble pools (etching/dissolving).
Greater than 0.6 is suggestive of problems for all pools (scale).

So depending upon how long the levels remain at those levels, you can understand why the calculator becomes such a valuable tool for us at TFP. Either way though, you appear to be in a safe area with those numbers.

- - - Updated - - -

If your CH was 350, TA remained at 100, and pH 7.6, your CSI would be 0.01 - almost perfectly neutral.

 

[Dparnell]

Pat,

I added some calcium chloride yesterday. I was able to get some pictures of the streaks and blotches this morning. I also re-tested everything.

Are these streaks signs of scale? Not sure if you can see the streaks in the pics.

CYA - 90
CH - Now 400
TA - 100
PH - 7.5
CL - 6 (looks like I lost some over night)

[/URL][/IMG]

[/URL][/IMG]

[/URL][/IMG]

[/URL][/IMG]

 

[Dparnell]

Looking at them now it looks like a poor acid wash job. Could that be? If so, why would it become more noticeable as time goes on?

 

[bdavis466]

I wish you hadn't added the calcium. There was no need for that.

The discolorations are from areas where the acid wash didn't completely remove the excess plaster to expose the aggregate. Since you did a bicarbonate startup, the water was never aggressive enough to remove it either. By having the water oversaturated with bicarbonate you sacrifice a little color uniformity but gain longevity and a smoother surface in return.

You might notice the color of the plaster lightening up as well. Unfortunately most of the plaster color pigments are organic and are eventually bleached out from the chlorine. Blue is the most susceptible color and is very notorious for losing its pigment.

So long as you haven't allowed the pH to drift above 8.2 for an extended amount of time, scale really isn't a remote possibility and it would have shown up at the waterline long before on the actual plaster surface.

 

[Dparnell]

Brian,

Is there anything I can do to achieve a more uniform appearance? Since I did add the calcium chloride should I do anything else?

thanks

 

[bdavis466]

A stainless steel brush may help a little and with time it could even out. If the areas are really bad you can put some acid in a bottle, swim down and hit the areas you want to even out.

Pay close attention to the CSI since your CH will be riding very quickly over the next few months.