What is this rust spot?

[pc132]

Hello,

We haven't used our pool regularly in a few months, and during that time, I've noticed a rust spot on the bottom. I thought perhaps it was just a piece of metal, but I finally got a chance to dive in a get a closer inspection and it's not something I can just take out of the pool. It's a rust spot flush against the bottom of the pool. The spot where the rust is has sort of an indentation, and i'm wondering if if the plaster has been somehow eaten away to the point of showing the concrete underneath. But would that cause rust? Anyhow, words probably don't adequately describe it, so here are some links to videos I took with an action cam. The scraping is b/c I took one of those pumice stones when I thought it was just rust. Any ideas what this is and how to remedy?

Picture: New photo by Paul Cho

Thanks!

 

[mknauss]

Take a handful of vitamin C tablets, put them in a thin sock, crush them up a bit, and set on the stain. If it goes away, it is rust. Most likely there is rebar near the surface that is bleeding through.

 

[ajw22]

Probably rusting rebar with the rust migrating to the plaster surface.

Take a strong magnet and see if it sticks to the area?

How old is the plaster?

Fix is to drain the pool, chip down tot he rusting rebar, cut it out, fill the hole with hydraulic cement, and replaster the pool.

 

[pc132]

Thanks! Pool and plaster are just under 8 years old. I did some searches after the replies and it seems that this is not exactly uncommon. What causes it? I live in Southern California, and we have had minor earthquakes here and there, so perhaps that?

Also, do these things generally fall under warranty? I believe I recall that the steel is covered for 10 years, but not sure if this is a part of that.

Thanks so much!