One black spot, been growing slowly for about 3 years. What is it?

[tampapools]

It's maybe an inch wide at this point. I looked up pictures online of rebar rusting and they all have orange rust stains. I also looked up pics of black mold, and they seem to have many clusters, not just one.

This is a pure black spot, growing very slowly. I touched it and it feels exactly the same as the surrounding plaster, no difference in texture.

Any idea?

 

[mknauss]

Have you tried some Vitamin C tablets in a sock?

 

[tampapools]

I haven't attempted to fix it. I'm planning to call a few pool refinishing companies to give me an estimate (pool built in 2003 and has some surface etching), then asking what they think about the black area, but given that they're going to be sales people, I figured you guys could give me an unbiased opinion.

I was afraid to scrub it in case I make it worse. Could be spreading something around or damaging it.

 

[1poolman1]

It does look like rebar bleed through. Could also be a piece of tie-wire that was too near the surface and is starting to come through.

 

[tampapools]

just had a pool resurfacing guy come over, and he didn't have a clue what it was either.

 

[kul]

I have a similar spot on my pool wall that I just noticed today. Vitamin C didn’t really do anything and neither did a Trichlor puck or intense scrubbing. Mine is currently the size of a pencil eraser and I’m not sure how long it’s been there. I plan to keep an eye on it to see if it changes. Keep me posted on what your spot might be.

 

[Dirk]

I had a similar spot that was fixed under warranty. He fixed it so fast, like 10 minutes, I never got to see what he did. I got a phone call and he was done and gone before I got off the call! I assumed one could not fix a rebar issue that fast, so I just figured it was some errant bit of iron in the plaster/pebble-mix itself. I think he just dug out a chunk of the plaster and then patched it. Never came back, and I can't see the patch.

If it's something simple like that, so will the fix be.