Scaling?

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1051dvl

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Jun 23, 2011
13
Atlanta, GA
New replaster - help me assess this situation

Relatively new pool owner and need help assessing my situation. First, the stats:

FC = 4
TC = 4
pH = 7.4
TA = 70
CH = 300
CYA = 60

Just had my IG pool replastered in white as part of a very long, frustrating renovation process (poor contractor). After the replaster work, the contractor became completely unresponsive, so I was left on my own, but managed to follow all the research/advice I could gather here and elsewhere about the start up process (twice daily brushing, no salt for 30 days, minimal chlorine via floaters, kept pH in check).

All looked good until about 6 weeks post replaster, when these “stains” started to appear, and now cover a number of areas, most apparent in the deep end, especially where the walls meet the floor, although lighter versions can be seen on the floor elsewhere (most visible on cloudy days, in the shade). No amount of brushing, even with a wire brush, has an effect. Surface is smooth.

http://s1186.photobucket.com/albums/z373/1051dvl/

So, is this much discussed mottling or something else? While I might accept some of the lighter variations as normal mottling, the darker, more pronounced areas seem like something I've never seen in a white plaster job and not normal. It looks a little like dirt, but does scrub or bleach out. Again, the contractor won't return my multiple calls and his business number is now disconnected. I have no hope that I'll get any resolution with him, so reaching out to you guys for support.

I look forward to your thoughts and advice...
 
Re: New replaster - help me assess this situation

Welcome to TFP!

One easy test to get more information is to hold a vitamin C tablet against one of the mottled/stained areas for 30 seconds and see if that makes any difference. If the vitamin C tablet improves things you have metal staining, most likely iron. If it doesn't have any effect we have at least narrowed down the list of possibilities.
 
Re: New replaster - help me assess this situation

Yep, forgot about the Vitamin C test. I did that test and didn't see a change.

As one additional data point, I just got back from the local, usually reliable pool store (actual experienced adults working -- not Leslie's). I showed the pics to one of the guys and his first impression was that it was scale. But, I was thinking that scale would be rough to the touch, which this isn't. Does that change anyone's view? Any suggestions on battling it if it is fairly fresh (~2 week old) scale?

Thanks again
 
My guesses would be:

1) Excessive use of calcium chloride (used to accelerate the speed of the plaster setting and curing).

2) Trowel burn due to excessive hard trowelling (more likely if excessive calcium chloride was used or if plastering during excessive temperatures, as the plaster might set too quickly).

3) Adding water to plaster while hard trowelling (again, more likely if excessive calcium chloride was used or if plastering during excessive temperatures, as the plaster might set too quickly).

4) Calcium Silicate Hydration due to lack of brushing and/or improper chemical balance. Calcium hydroxide created during the curing of the plaster can become calcium silicate hydrate if the pool is not brushed and/or the chemicals are not kept in balance.

Unfortunately, none of these causes are easily remedied (if they can be fixed at all).
 
Thanks for the reply.

I'm pretty confident that calcium chloride was not added during the plaster process. The project was completed third week of May (temps in the high 70s- low 80s) and I had a very explicit discussion with the plaster crew foreman about this as he was preparing the mix. I had previously read about the risks of calcium chloride and was trying to be proactive about the issue.

Any more details about your improper chemical balance point? I managed the start up chemicals personally and have a good log of the activities and test results.
 
Ok, here are the gory details:

It was a four-man crew (1 working the mixer on the truck, 3 in the pool). Seemed to be fine with no signs of difficulty in working the plaster. Again, the finished looked good and consistent for the first four weeks, then the staining started to appear.

And the high-level process I followed:

Days 1, 2, 3 -- fill (city water -- 2 hoses, continuous flow), started brushing once completed filled.

Week 1 - Chlorine tablets added via floating dispenser on Day 4 -- water very clear, but wanted to maintain minimal chlorine (tested less than .5). Added first bottle of stabilizer. PH off the charts, but started to get under 8.0 after I added about 2 bottles of acid. Was adding a bottle every 3-4 days. Daily, often twice daily brushing. Again, water remained very clear -- surprisingly very little, if any dust stir up/cloudiness, which struck me as odd.

Week 2 and 3 - FC stayed around .5, PH fluctuated between 7.2 and 8.0 (kept adding acid every 4 days or so to stay under 8.0. CH very low -- added 10 lbs of calcium flakes (not sure what product is called). More daily brushing. Water very clear -- plaster looked good, but some lighter and darker white areas, but seemed with the range of normal mottling.

Week 4 -- same activities (maintain minimal chlorine, focused on keeping PH under 7.8. At end of week, took first real battery of tests:
FC - 1
PH - 7.2
CYA - 30
TA - 30
CH - 170
At that time, added 20 lbs of more calcium -- good brushing to dissolve. Later that day, added salt to achieve 3200 ppm -- good brushing to dissolve -- started up SWG

3 days later test results:
FC - 0
CYA - 30
PH - 7.2
TA - 40
CH - 240
added another 10 lbs or so of calcium

Next day, limited tests:
FC - .5
PH - 7.8
CH - 310
added 1/2 gal of muratic acid

4 days later:
FC - .5
PH - 7.2
TA - 30
CH - 300 (validated by pool store test)
Concerned about SWG not working, tested at pool store -- all clear. Added shock, more stabilizer, and baking soda per pool store instructions
Started to notice initial staining... tried wire brush on sections, but didn't seem to work.

Next day:
FC - 5+
PH - 7.0
CYA - 60
TA - 70
CH - 310

From then until now (1.5 weeks): FC has dropped to 2-3 range, PH has spiked to nearly 8.0 once, but ranged 7.4-7.6. Visited pool store today and added some additional stabilizer per their instructions as well as bottle of scale inhibitor. Increasingly apparent staining (or I'm more sensitive to it!).

Pool store results from today:
FC - 2
TC - 2
PH - 7.4
CYA - 50
TA - 73
CH - 318

Does this help?
 
I think that you probably did the startup OK.

Without being able to see the plaster, it's hard to tell from pictures. It is not unusual for white plaster to not be perfectly white. Plaster uses natural materials, which will have some variation in color.

You could contact the National Plasterer's Council at their questions page and ask them for their opinion.

They can even do an inspection if you want. Reference
 

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Is it possible this could be dirt and/or algae that somehow got embedded into the new plaster during the curing process? If you look at my start-up details above, you'll see that my chlorine level was pretty minimal during the first 30 days (less than .5 or so).
 
Real time update....

After leaving a chlorine tablet on top on a portion of the affected areas for about 4-5 hours, the stains have lightened considerably. What does this tell me and how can I effectively go about treating the entire pool (20'x44')?

Current FC reading is ~3.
 
I put 6-8 pucks on the plaster floor a few inches apart, leaving for 3-4 hours with good effect -- the stains cleared. It was a slow process, but after a few days I was able to take care of about 25% of the pool.

During this time, I turned by SWG to 0% as I was getting plenty of FC from the pucks. But I removed the pucks for 4 days as I was busy and traveling, turning the SWG back on once the puck-sourced FC dropped down. pH ranged between 7.2 and 7.4 during this period.

Now, after being out of town for 2 days, I can see the "staining" or scaling or whatever reappearing in the areas I had cleared with the pucks. Really would appreciate your help trying to figure out what's going on here. The only variable that changed seemed to be use of the SWG - is that a clue?
 
Interesting. When I put those into the Pool Calculator I get a CSI of -.26, which I think tends to imply that it's not calcium scale. And the pucks clearing it tends to suggest something organic. Beyond that, I've got no clue. Hopefully one of the experts will be by and have some insight.
 
From the pictures provided, it appears that it is "excessive gray and white mottling." JamesW first post above indentifies the most likely causes with his #1, 2, and 3 points. The plaster material can be tested for "calcium chloride" content to see if plasterer/mixer added it anyway, despite being asked not to.
 
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