Unusual Star Trek Stains on plaster

[ComputerGuyInNOLA]

I started getting some stains on my plaster late last year. The stains started with one then others started popping up and now I have around ten of them. Each is shaped just like the Star Trek logo that was used on their shirts in the TV show. They do not respond to Vitamin C or a chlorine tab. They are not rough to the touch. I am starting to get worried because more and more are appearing. My current test from yesterday yields

PH 7.8 ( I know it is a little high but I ALWAYS keep it between 7.4 and 7.8)
FC 4
CC 0
TA 70
CH 230
CYA 55 (Both tries were right between 50 and 60, I know it is a little low but we have had a LOT of rain)

I called my pool builder last week. He sent a guy over within two hours but the guy seemed stumped. He asked if we had used the metal out that was provided when the pool was built and I told him I had. He asked if we were adding more every month and I told him I had not. I told him I tested for metals every six months at a local pool store and had never had any metal present so I did not see any need for it. He said that since there was metal in the gunite I should be adding it and that may be the cause of the stains. I told him that since the plaster was supposed to be waterproof how could rebar in the shell bleed through like that. He had no answer. I also have one small spot of plaster about the size of a dime that has turned completely white on the grey plaster. He took some pictures and said he would show the owner and get back to me. It has been a week but no response. Any ideas out there?

The stains are all shaped just like this and are light brown.



Here is an image without modification and you can see one on the top left and the bottom right. You can also see several smaller ones in the center but they have the exact same shape.


This is a close up shot that has been modified to improve contrast.




Thanks for the input!

 

[yardoasis]

Maybe the USS Enterprise paid a visit to your pool without you aware?

Just kidding! I'll follow this one, this is an interesting question. I, too, am dealing with a more pervasive plaster problem, and I'm going to my PB about it.

 

[jtech1]

How old is the pool? Do you have pictures from when it was built? I'd be curious if there was any rebar at those points that was sticking out and may not have gotten at least 2-3
" of gunite coverage? To be that localized, I'd think the rebar would have to have been very close to the surface of the gunite at those points if it were the cause. Pictures or video of them shooting the gunite may be helpful to see how much coverage the rebar got. Or possibly metal ties that were not bent down, but sticking out?

 

[Bama Rambler]

It looks like rebar stains, but those should respond to vitamin c unless they used copper coated rebar.

 

[onBalance]

Stains like that would not be from metal dissolved in the water. Are any stains on the wall, or just on bottom surfaces?
Make sure you don't have a small piece of metal moving around the bottom of the pool staining a different spot each day.
I suggest trying to sand the brown stains with some 100 grit wet and dry sandpaper.
Is the white spot rough to the touch?
Pool Plaster is not 100% waterproof. More like 98-99%. It will allow a very small amount of water movement through it.

 

[jblizzle]

Looks like what I have from a hair tie that moved around the pool ... No more of the ones with metal allowed.

 

[ComputerGuyInNOLA]

Thanks for all of the input. The pool was built in late 2012. We never have anything on the bottom of our pool for more than a few hours at most. We look at our pool every day and manually net what is not picked up by our Polaris. We do not fertilize our back yard due to the known problems. The strange thing is that all of these anomalies have the exact same shape. It looks as though a piece of metal was left on the plaster and that water movement passed over the piece of metal but many of these stains are in areas of little to no water circulation. One of these is in a corner with no water circulation. We live in South Louisiana so our pool is open year round and we monitor it daily.

Onbalance, I was hoping you would see this after seeing your post on mottling which is another issue I am having but would rather address after solving this issue. The white spot I referred to is as smooth as the plaster. If you run your finger across it you would not know it was there. It sticks out like a sore thumb because it is the only white spot in the pool. It showed up about a year after the pool was plastered.

 

[jtech1]

If the rebar ties were done sloppily, not bent down, and not covered adequately with gunite, I could see them making that shape... but only if they were REALLY close to the surface. This is not a great example since it is double tied, and I doubt they double tied them... but if a single tie were not completely twisted it could have a V shape also.

 

[ComputerGuyInNOLA]

Ktech, I am going to find the pictures of my build. I took a lot and I have pics of the rebar.

Onbalance, all of them are on the bottom.