Quote Originally Posted by JimK View Post
Several years ago when having problems with stains, probably iron, I got rid of the stains using ascorbic acid (I forget the exact procedure) and started using Jack's Magic Purple Stuff to keep the stains from returning (initial dose of 2 qts, then 12 oz each week in my 20k gal vinyl IG pool). I've been using it for several years now and they stains have not returned.

Speaking of using HEDP sequestrants, I understand that chlorine breaks them down. Ben, does that mean that my regular addition of HEDP (I add 12oz of Purple Stuff each week per instructions) is increasing chlorine demand? I wondering if by using this product I'm shortening the life of my salt cell?

Something else I don't understand. I know the HEDP sequestrant keeps the metals in solution, but you mentioned that as it breaks down the metals will end up in the filter? The Purple Stuff I use claims it allows the filter to trap the metals so they won't stain the pool. Does this mean that is some indirect way the HEDP helps remove the metals via the filter?

BTW, I'm in the process of testing my pool for metals using your bucket technique you suggested. I'll let you know the results.

Thanks.
After the first step (add 1/4 cup bleach to 4 gal of water, then wait 24hrs) of your suggested "bucket test", I don't see any staining or anything settling out in the white bucket. I added the washing soda today and will check on it tomorrow to see if anything shows up.

Is it possible that all these seasons of using the Purple Stuff (or my use of cal hypo to shock on a regular schedule?) has removed the metals from my pool? I find this puzzling as it seemed the source of iron was from the salt, which I still add (I go through about 150-200lbs per season on average). Any ideas?

Ugh.....it's giving me a headache trying to figure out exactly what I should be doing to prevent metal stains from returning without throwing away money on stuff I may not need. Don't know if this is possible without just experimenting and see what happens (I really don't want to have to clean a stained pool again!).