Vinyl Liner Staining from metals??

[Jcarmic]

Been following this site for years, absolutely love it, joined 3 years ago and have never got to the point that I needed to post.....until now.
Problem is staining of vinyl liner inground pool. Have had pool for 22 years and only for last couple I've been challenged by staining that appears to be from metals b/c Ascorbic Acid treatment completely removes all stains instantly. I've followed all advice from these forums, AA treatment, Jack's, low ph, slow chlorine increase, etc., and stains eventually come back, primarily on steps (dark yellow/brown). Last two years at startup I even drained about 6000 gallons out of 29K gallon pool and had clean water delivered in attempt to dilute whatever metals existed. No such luck. Also, there is a very large Oak Tree next to/hanging over pool....I've read here that Oak is worst to have near b/c it contributes to metals in water...ugh. Haven't taken it down yet b/c it probably cost me $5K.

I bought metal test strips, Copper and Iron, always have shown zero....last week I broke down and brought water to pool store for metal test....it came up 0. At first pool guy said I had zero metals, then said that b/c chlorine is high (FC =12, CYA =53, PH=7.4, TA = 85) metals won't appear in testing. Is that true??? I already had stains and was getting some algae, so followed SLAM, that's why FC is currently high. Pool's already stained, so I wasn't concerned about that vs algae. Another guy there tried to sell me Calcium and said that could be the root cause of staining. I don't buy that based on EVERYTHING I've read on all of these forums. My Calcium is 180....he said I need to bring it up to 350 or so and I should bump up TA to about 150-200 and that would help staining.

Summary questions are
Does high chlorine prevent accurate metal testing and if so how or when can I get an accurate read?
Can anything other than metals cause this kind of staining on vinyl? Again AA removes it everytime with no problem.

Thank you!!

Brief update, I've not added chlorine since Thursday night (3 nights ago), Chlorine down to 8.5 now. Likely going to do AA treatment again, but hoping to get some insight before doing that again. Thanks!

 

[mknauss]

Welcome to the forum!

does high chlorine prevent accurate metal testing and if so how or when can I get an accurate read?

A FC of 12 is not high. So it is not effecting your testing.

Can anything other than metals cause this kind of staining on vinyl? Again AA removes it everytime with no problem.

If AA removes it, it is iron. It may not be at a level you can test for it as it is on the walls of your pool.
To remove it, you need to do the AA treatment, and then drain the pool and fill it with iron free water. Or devise a filtering system for when the iron is soluble in the water.
I suggest you read ABC's of Pool Water Chemistry.

 

[Jcarmic]

Thank you very much. I have read through the ABCs and that's what has helped me so much over past few years, just that the pool guys' explanations did not seem viable, yet they were definitive in their opinion. That's why I came to you.

Am I correct in thinking that after I do the next AA treatment, the iron will then be back in solution and could be identified via testing? I'm curious as to how much iron there is b/c as mentioned, I've drained and refilled 7k gallons for the past two years.

Are you suggesting that a complete drain and refill would be what I need to do? If so, would it make sense to wait until spring given I only have a couple weeks left here in MA.

Thanks again, truly appreciate the help!

 

[mknauss]

You cannot completely drain your pool without great risk of damage to the liner.
It may reach testable levels after an AA treatment.

Read Iron Fill Water Filter - Further Reading for methods to remove Iron when in the pool water or from your fill water.

 

[Jcarmic]

Thanks, I thought that was the case which is why I only drained some. I'll try more next spring. I'll read that link a little later.

Again, thanks a lot for your help, very much appreciated!