Is it Metal?

[AOR]

For the last 2 years I have had a dark, shade-like stain only in the deep end of my fiberglass pool. Does not seem to scrub off with abrasive sponge, etc. Seems to spare the very edge of the pool corners. I theorize due to the accumulation of chemicals in the corner of the pool that "bleaches it" but this is a guess. I am not certain when it appeared in relation to the addition of chemicals. I had added an algaecide from Home Depot prior to close a couple years ago, so I postulated it maybe copper and related, but not sure as it was overwintered then.

I took a sample to the pool store to discuss with them about 2 years ago and they said the "metal" was a bit high, and I used a sequestering agent. On retest I was told it was fine.

Stain remains.

I included a picture. Is there anything I can/should try? I suspect this is just cosmetic but it bothers me.

Thank you, and best regards to an awesome site.

- AOR

FC = 3.5
pH = 7.5
TA = 150
CH = 130
CYA ~ 40
Borate = 30

 

[pooldv]

Welcome to TFP!

Crush up some Vit C tablets in a sock or knee high and rub it on the stain for up to 30 minutes. If it lifts the stain then it is metal. If it does not then rub a trichlor puck on the stain for up to 15 minutes. If the stain lightens then it is organic.

For a metal stain read up here, there is a link to an Ascorbic Acid treatment page that can lift the stains. Pool School - Metals in the Water and Metal Stains

For organic stains raise FC up toward shock level, [FC/CYA][/FC/CYA], and brush. The stain should clear up in a week or two.

 

[YippeeSkippy]

First I would suggest you stop using abrasives on the pool- that is if you want to protect your gelcoat surface that is?

Grab a handful of vitamin C tablets and put them in a sock and rub it on one area. If it lifts the stain its metal.

Then in a different area try holding a chlorine puck on the stain and if that lifts it after a few minutes, its organic.

Let us know what you results are.