Need help clearing scale off Pebble Tech

[Chandra R]

My pebble sheen finish is the black/darkest they carried at the time wenjnstalled. Over time (it was installed in 2009, the finish has been problematic. The pool company came out and did a no drain acid wash several years ago and that darkened everything up for awhile, but this summer we started to see lots of light patches and I was told by them that it should be done again. We are no longer under warranty and they told me to look it up online - so I'm attempting to take care of it myself. I have put a total of three gallons of muriatic acid in (two gallons this week and one gallon today) and here are my latest results:

FC: 5
pH 7.2
TA 50
CH 230/240 (I have a hard time reading this one)
Water temp is 45 degrees.

This puts my index number at -.9. I believe I see
Some improvement but the sun is at such a lower level that it's hard to see it as clearly as in the summer.

My questions are: how long is it okay to leave the index that low? I do not have a heater and my pool does run because of frost protection. I don't want to harm the surface
But I don't want to bring it up too soon and not accomplish the task.

There are significant white streaks in the deep end and a dark streak that I fear is black algae, which I dealt with a bit this year (and that was a total pain).

Thanks in advance for your help!

 

[bdavis466]

An acid bath is accomplished by adding several gallons of acid per 10,000 gallons of pool volume. The goal is to lower the TA to 0 which will leave the pH around 4.

Your current CSI is not low enough to have any immediate or noticable improvement to the plaster. Given the numbers posted above and if you've maintained your water similarly to those numbers, scale is unlikely. I think what you are seeing is mottling of the plaster.

Are the areas raised and rougher than the surrounding areas?

 

[gwegan]

The darker colors will fade more than lighter colors.

Acid washes remove the top level of cement and leave "fresh" plaster which starts the fading process all over. Each time you acid wash you reduce the life of the plaster.

Premier is no longer the Pebble Tec vendor in Sacramento. You might call the current vendor and ask what they think.

 

[pooldv]

More here, The Zero Alkalinity Acid Treatment

 

[Chandra R]

Premier is no longer the Pebble Tec vendor in Sacramento. You might call the current vendor and ask what they think.

So was Premier the only vendor? Do you happen to know who the new one is?

- - - Updated - - -

An acid bath is accomplished by adding several gallons of acid per 10,000 gallons of pool volume. The goal is to lower the TA to 0 which will leave the pH around 4.

Your current CSI is not low enough to have any immediate or noticable improvement to the plaster. Given the numbers posted above and if you've maintained your water similarly to those numbers, scale is unlikely. I think what you are seeing is mottling of the plaster.

Are the areas raised and rougher than the surrounding areas?

So what is the mottling caused by and is there anything to do to help it? I have felt like the pebble surface was rougher this year but maybe I'm getting more sensitive in my midddle age

 

[pooldv]

Rougher plaster could be caused by scaling or etching. More here, Pool School - Calcium Scaling

More here about mottling and other plaster issues, Diagnosing Pool Plaster Problems

 

[captjoemcd]

How do you shock your pool? Do you SLAM with liquid bleach or add cal-hypo?

I went through this last year and tried the no-drain acid wash twice, but it was unsuccessful - there was just too much scale (calcium carbonate) on the pebbletec. I ended up doing a drain and acid wash and the results were dramatic. I had scale (white streaks on the first picture) from cal-hypo on top of dirt. I was able to remove the dirt with a pressure washer only after the acid wash - the pressure washer didn't touch the scale. Lots of brushing removed the dirt after the acid washing removed the scale, but the pressure washer was a lot quicker/easier. The second pic shows dirt on the left after acid wash and dirt removed on the right after pressure wash following the acid wash.

 

[captjoemcd]

Also - the reason I ask about cal-hypo is that even though your chemistry wouldn't suggest scaling conditions, it is possible that adding chemicals results in locally much different chemistry (for example, much higher pH and calcium concentration from particles of cal-hypo sitting on the bottom of your pool). This was one of my inherited issues from my pool's previous owner.