Rust Colored Stain Around Water Outlet

[Kit]

I have a rust-colored stain around the small water outlet (not the jets) in my in-ground spa. My initial assumption was that the iron content of the water was high. But we are on city water, as opposed to well water. Any thoughts would be most appreciated. Thank you so much.

 

[JohnT]

Iron is still a possibility. Rust water lines can add it even if the source water doesn’t have it.

 

[Kit]

If the culprit is indeed rust, I believe that I read in Pool School that applying a sock with 15-20 vitamin C tablets against the rust area for 15 minutes will decrease or remove the rust. Does this seem correct? Is it necessary to drain water in the spa to expose the rust-colored areas prior to applying the vitamin C? Thank you.

 

[mknauss]

Does this seem correct? Is it necessary to drain water in the spa to expose the rust-colored areas prior to applying the vitamin C?

That is correct. Put the tablets in a thin sock and crush them a bit. No need to lower the water. Just press / rub the sock around the stained area.

 

[Kit]

Thank you. I will try it.

 

[Kit]

Tried the vitamin C tablets in the sock trick. It initially dissolved about 40% of the rust-colored stain immediately upon contact. Then after about 5 minutes of rubbing, the remaining stain was unaffected. With that said, I have a couple of questions:

1. Assuming that indeed the stain was rust, is there an alternative method to dissolve the remaining rust (e.g. a more concentrated form of ascorbic acid)?
2. Might the stain be caused by something other than rust?

Thank you for your help.

 

[mknauss]

You can buy Ascorbic Acid in bulk. You can treat the entire pool volume if necessary Ascorbic Treatment to rid Pool of metal stains

If AA removes the stain, it is iron. If it changes its color, it can be copper or silver.

 

[Kit]

Since I only have the stain at the bottom of the single water outlet, I see no need to treat the entire spa. I will try another application of crushed vitamin C. Thank you.