Stain on Vinyl liner - what is it?

[MITBeta]

Hi Everyone,

I've been lurking here for a few weeks after stumbling upon this site while trying to understand the breakpoint chlorination section in my Taylor test kit manual.

I have since adopted the TFP way, completing my first SLAM about 10 days ago and finally solving the mystery of why my filter kept plugging up all last season, despite clear(ish) water. Spoiler alert: it was algae.

Anyway, I noticed when I opened the pool this year that my liner has a couple of reddish-brown stains on it, the bigger about the size of a quarter.

Can anyone advise what would have caused this? Until this year we used cal-hypo to shock weekly, and the stains are as far from the deck as possible, so this area doesn't get brushed as well as the rest of the pool. Could cal-hypo crystals cause this? Is there a way to remove them?

Thanks in advance for your help.

 

[Donldson]

Is this on the bottom or on the side? If on the bottom it sure looks like rust, as if a screw or something sat there over the winter. Does your cover have grommets on it and, if so, are any missing by chance?

 

[MITBeta]

It's on the bottom. I don't see how a cover grommet would have found its way to the middle of the pool, but anything's possible. Presently folded and stored away for the summer.

My pillow has grommets and definitely spent some part of the winter on the bottom of the pool. It has since been trashed.

I did not fish out any grommets.

If it is rust, is there any treatment?

 

[borjis]

I got two little rust spots too. Water isn't warm enough to get in yet, but try a sock with crushed vitamin c tablets resting there for 30 minutes. That usually works.

 

[DiverGirl1972]

I have the same issue, especially around one of the main drains in the deep end.... All of those spots in the stain 1 picture are rust-like spots. I know nothing has ever sat on top of the liner under my watch and it's gotten worse in the past couple of years since we bought the home, so I have to believe it's something underneath. Not trying to hijack your thread because I've kind of given up on it for now. I did strap on a scuba tank last year and tried putting crushed vitamin c (and a puck) on the stains for a bit but it didn't affect it at all, which was surprising.

Anyway, it's really annoying but you're not alone! I'll be watching to see if you have luck making them disappear.

 

[MITBeta]

Vitamin C tablets like these?

 

[DiverGirl1972]

Yes, but some other brand... Nature something or other, but vitamin C. I don't recall the MG in each tablet, but I poured a quarter of the bottle out, crushed it up, put it in a thin sock and headed down to the bottom for a while and had no luck. Idk...definitely didn't do it for 30 minutes, but I probably did it for 10 - 15 minutes... Maybe I didn't do it long enough. Perhaps I'll try again this year, seeing as I don't see a scuba trip in my future any time soon! lol

 

[MITBeta]

Tonight I crushed up a bunch of Vitamin C tablets, tied them into a filter sock and applied the sock to the stain for about 10 minutes. There was no change in it.

I've read that calcium hypochlorite can stain vinyl. What do those stains look like?