Dark Stain on Plaster from Chlorine Puck

[salty87]

Part of a chlorine puck (Trichloro-s-triazinetrione) ended up in the pool for a day or 2. Once removed left behind is a dark stain on the plaster.

I've read about vitamin c for iron. Is there anything that can remove the puck stain?

Thanks

 

[Donldson]

Can we get you to share a picture of the spot and of the container the puck came in?

 

[salty87]

Absolutely. The small stuff is just whatever debris, I hadn't swept yet. And, the spillway was running so a little turbulence on the water. Other than the 2 greyish blobs the plaster is fine.

Thanks

 

[Donldson]

That's interesting. Trichlor typically bleaches out a finish, but that looks more like some sort of metal staining.

Do you use any kind of algaecide or added anything else to the pool we wouldn't typically recommend? Not looking to berate, just trying to help you figure out what caused it and whether there's a simple solution.

 

[JamesW]

I would suspect copper stains.

 

[salty87]

Nothing else added except a little acid every now and then to keep pH down.

Pre-pandemic I used bleach but it's become expensive and sometimes hard to locate. CYA level is a little low so I've been using pucks lately. Pool was originally filled by truck in 2016 but since then the level is maintained with rainwater. And, at least 1/3 of the water was pumped out and replaced with rainwater a couple years ago. The rainwater tank needed to be partially emptied for some maintenance so this was an opportunity to knock CH level down.

 

[onBalance]

I suggest using 100-grit wet&dry sandpaper to remove those stains.