Weird Spots/Discoloration

[batterfierd]

Over the past 6 months, my pool has begun to develop spots. These sports are at the bottom of the pool, in both the deep end and shallow end.

I do not have any items falling in the pool (coins, nuts, etc.). I get the regular leaves, but I have a Hayward pool vac that runs daily.

I've tested my water consistently over the past several months, even bringing in samples every month to a local pool supply store for them to verify and check additional things. My pH is good, chlrine is good (it's a salt pool), TDS, Phosphates, Alkalinity, calcium, etc. Everything seems normal.

A wire brush will not scrub these off either.

I'm attaching pictures. I have no idea what this is, I hope somebody here does.

Thanks in advance!

 

[UN1017]

Have you checked to see if it's iron staining with the Vitamin C tablet test? Did you previously have issues with a corroded out heater?

While you're at it...can you post a set of current test numbers just to make sure.

 

[batterfierd]

Sorry this took me a few days to get to the full tests. So the Vitamin C tab just seemed to wear down from the surface (I believe it's pebble tech) and didn't do anything to get rid of the spot.

Here are the results of my test today:

Free Chlorine - 1.5
Total Chlorine - 1.5
Salt - 3000ppm
Calcium - 460ppm
Cyanuric Acid - 50ppm
Total Alkalinity - 80
pH - 7.8
Copper - 0
Iron - 0
Phosphates - 150ppb

 

[jblizzle]

Are you sure it is not just a group of dark colored stones in the finish? Hard to tell in the picture.

I have a few spots that are whiter just due to a bunch of white stones next to each other.

 

[batterfierd]

I'm sure. They were there a few months ago, and more are popping up here and there. I have the high-res file, but can't post here. If you think that would help, I can post and link.

 

[onBalance]

How old is the plaster job? And is it a re-plaster.

 

[batterfierd]

I dont know. The home was built in 97, and I moved in last year. I'm not sure if the pool was put in when the house was first built, or added afterwards. It's pebbletech, but are you thinking that it might be wearing through? Is that rebar we're starting to see show through?

 

[onBalance]

No, I don't think it is rebar or the substrate showing through. I am thinking maybe the pebble tech plaster surface has some very small cracks where a calcium scale deposit forms. Has the pool been drained recently?

The pebble tech surface might be a new layer of plaster over the old plaster surface. Are the small discolored spots really rough to the touch? And are they raised above the surrounding surface?

 

[batterfierd]

The pool has not been drained recently as far as I know. I certainly haven't drained it. My calcium readings seem to be within normal ranges. I'm not sure if the spots are rough to the touch, but I'll check it out. It's odd though, because these started showing up earlier in the year and just seem to be growing in number.

 

[Casey]

Free Chlorine - 1.5
Total Chlorine - 1.5


Cyanuric Acid - 50ppm

I think your chlorine is too low.

 

[onBalance]

It is possible that you are getting "calcium Nodules" which is a delamination of the new plaster surface from the underlying substrate.