Algae?

[mbeck5]

Good morning,

Been following TFP for several years and everyone in these forums has been generous with time and good advice. Last week I noticed what looked like 2 rust spots on the bottom of my pool about 1 1/2 inches long and 3/4 of an inch wide. I checked with my snorkel mask and plastic scraper and closer up, the majority of the spot looks brownish with some yellowish tinges around the edges. Scraping did nothing and I am wondering if anyone can help me identify what these spots are and what to do about them.

 

[zea3]

They look more like rust stains. Try crushing some plain vitamin C tablets in a sock and lay it on the stains for an hour. If it is rust it should lift the stain.

 

[mbeck5]

Thanks zea3, will give it a shot, appreciate your help

 

[cowboycasey]

it looks to be inline so it may be a piece of rebar that was close to the top of the concrete...

 

[mknauss]

Then take a strong magnet and put over the spots. They are most likely from the wire ties used on the rebar. This will reoccur often if that is the issue.

 

[mbeck5]

Makes sense, will try it Rebar coming through can’t be a good thing Is this indicative of plaster erosion, water issues?

 

[mknauss]

Your pool shell is 60 years old. If rebar was close to the surface of the shell and the plaster is not very thick in that area, the iron can bleed through. Doubt it is wire ties if your shell is that old. I did not see that earlier.
You do not save any chemistry data in Poolmath so unsure about water issues.

 

[mbeck5]

I apologize for not responding with an update sooner. The crushed vitamin C tablets in a sock made a marked difference in the rust stain and we had the company that did the replastering
ten years ago inspect the surface. The result was pool surface is fine. Appreciate all of your help as always.

 

[mbeck5]

AND I got no response from magnets.