Odd stain on pebble plaster

[ECEGatorTuro]

We had an in-ground pool built and completed back in August 2020 and everything has been smooth sailing (chemistry-wise) until two weeks ago. I noticed a strange stain appear on the pebble sheen and can’t figure out what it is. I’ve tried scrubbing it hard with a stiff nylon brush to no avail. The chlorine level has been around 20-25ppm for over a week since I had recently added CYA (to get it back to 60) and forgot to turn down the SWG cell. There are no stains anywhere else in the pool and the water is auto-filled from our municipal source (Phoenix suburb). The only correlation is that we had several trees trimmed just before I noticed the stain and I know some large branches fell into the pool as I saw the arborists fishing things out of the pool after they finished. If the stain was organic, I would imagine scrubbing it and the high chlorine levels would have eventually removed it.

I’m out of ideas unless this is some rust that is coming from the rebar due to poor construction?

 

[YippeeSkippy]

Got a magnet? See if the stain and the magnet have an infinity for each other- if so it could be a bit of rebar showing thru.

Maddie

 

[Dirk]

The rebar is quite a bit behind the surface of the gunite, but even if it was very close, there's still another layer of plaster and pebble to get through. It's more likely a piece of iron in or attached to one of the pebbles. Snuck in during transport or during the mix. I had the exact same stain. Just the one spot, like yours. And had the same worry, but it wasn't rebar.

Might be a rebar tie wire, but it doesn't matter. It's an easy fix, and I'd advise you to stop trying to do it yourself before you make it worse. Your finish should be under warranty, especially if its a brand name. Call up the installer and have him come out and fix it. Don't do anything they could blame you for. My guy came out and when I walked away for a few minutes and then came back it was already fixed. I never did get to see how he did it. He did get in, that's all I know. I suppose I could find some sort of patch if I really wanted to, but it wouldn't be easy and I've never tried. Came out great.

Enjoy the warranty while you've got it.

 

[ECEGatorTuro]

The rebar is quite a bit behind the surface of the gunite, but even if it was very close, there's still another layer of plaster and pebble to get through. It's more likely a piece of iron in or attached to one of the pebbles. Snuck in during transport or during the mix. I had the exact same stain. Just the one spot, like yours. And had the same worry, but it wasn't rebar.

Might be a rebar tie wire, but it doesn't matter. It's an easy fix, and I'd advise you to stop trying to do it yourself before you make it worse. Your finish should be under warranty, especially if its a brand name. Call up the installer and have him come out and fix it. Don't do anything they could blame you for. My guy came out and when I walked a way for a few minutes and then came back it was already fixed. I never did get to see how he did it. He did get in, that's all I know. I suppose I could find some sort of patch if I really wanted to, but it wouldn't be easy and I've never tried. Came out great.

Enjoy the warranty while you've got it.

I don’t know why I never thought about calling the pool builder. They have a tech coming out next week. Thanks for the idea!

 

[Dirk]

Great. Let us know how it turns out. We loves a happy ending!

 

[generessler]

I'll just add that we get some stains with that shape and color; not quite that dark. Scrubbing like mad even with a wire brush does nothing.

I've also tried sprinkling and brushing cal hypo granules over them. Maybe a slight improvement; not much.

But after a couple of weeks they're very light and a couple more they're gone, only to be replaced by more in different locations. At any time we have maybe 3 or 4.

I'm about 98% sure they're caused by a specific kind of plant matter falling in the pool. We have dozens of big trees within 30 yards. The secret to happiness has been to learn to just to let it go....

 

[Dirk]

I'll just add that we get some stains with that shape and color; not quite that dark. Scrubbing like mad even with a wire brush does nothing.

I've also tried sprinkling and brushing cal hypo granules over them. Maybe a slight improvement; not much.

But after a couple of weeks they're very light and a couple more they're gone, only to be replaced by more in different locations. At any time we have maybe 3 or 4.

I'm about 98% sure they're caused by a specific kind of plant matter falling in the pool. We have dozens of big trees within 30 yards. The secret to happiness has been to learn to just to let it go....

Yah I had a stain like that as well. Different spot than the one I described above. I fretted about it for a while, couldn't treat it. Then it just disappeared. I, too, think it was something organic that the chlorine eventually took care of...

 

[Lccobol]

I have several stains like this. I thought it was the pool vac weights causing rust spots.