Metal Stain Treatment Procedure


Well-known member
Apr 23, 2008
I’ve read several posts here and would like some input on my plan of action...

I have a 16.5K gal vinyl lined pool, constructed 13 years ago. Normal opening procedure for the past few seasons has been to throw a floater with some pucks under the cover in late winter to keep pool from turning green. Around April 1 I remove cover and caps, start pump and vacuum to waste, then test/adjust levels and replace cover until it warms up a bit.

This year, I removed the cover for good on May 2, did not notice any stains at the time. They appeared along side of wall where returns are located and at base of same wall in deep end a few weeks later. Also noticed black and brown/bronze stains on the face ring of my SAm light.

Before I could address the stains, my 7 year-old MasterTemp failed so I installed replacement on June 6. (Incidentally, I replaced Intellichlor at the same time, I knew it was nearing end of its lifespan last year and my FC dropped to 0 just before heater arrived - checked diagnostics in IC40 and it showed lifespan was zero).

New heater and IC40 worked, so I turned my attention to pool stains, which had turned worse - my step section was now a uniform light brown below the water line. This is where it gets interesting...

I spot treated steps and SAm faceplate a few times with 100% AA powder, without noticeable effect. Ordered a CuLator 1.0 and Jack’s Magic step stuff and vinyl stuff. Threw CuLator in skimmer and added Jack’s per directions (pump off, FC was 3, pH was 7.2, CYA was 55). Steps whitened before my eyes, and over the next couple of days the stains on liner turned noticeably lighter and stains on SAm faceplate disappeared (hence I suspected copper was the culprit, although I didn’t inspect heat exchanger on old MasterTemp). Then the water clouded up, FC tested 0 and I screwed up - before doing additional research I added bleach - too much of it of course. Added 1.5 Gal of 10% bleach, FC rose to 5.5 and stains returned in part but were less pronounced (steps turned a very light tan, stains on liner appeared to darken back a bit and stains did not appear to return at all on SAm faceplate).

I now understand that this process will require more time and patience, that the clouding is normal, that I should add very little chlorine if any during the process, and that a polyquat can be used with phosphonic acid-based sequestrants to help prevent an algae bloom.

I’m planning to give this another shot after the July 4 weekend, and would appreciate any feedback...

As noted above, the stains returned but are not as pronounced. The step section has light tan/almost yellow stains below waterline. I just tested with AA and stain disappeared. Steps did not respond to AA before - only responded to Jack’s. Also, stains did not return to the SAm face plate. Very puzzled by this - is it possible that I had a mix of copper and iron stains, that the CuLator, step & vinyl stuff and filtering/vacuuming worked and that I was able to remove the copper and maybe some of the iron before I interrupted the process by adding bleach? (I added some DE to my sand filter via skimmer, ran pump continuously for two days and then vacuumed to waste before I added bleach).

Plan is to add polyquat evening of the 5th, let pump run for 24 hours, then add another dose of step and vinyl stuff on the evening of the 6th, add more DE to skimmer and patiently wait for a few days, doing little more than testing FC and pH and perhaps backwashing filter and adding more DE. Once cloudiness disappears I will vacuum to waste. What then? Add bleach, see if stains return and then keep repeating process until they don’t reappear? I have a vinyl pool, so draining and re-filling is not an option...
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Gold Supporter
TFP Guide
Jul 21, 2013
Northern NJ
Sounds like a good plan. You understand the tools available to you better this round then the first time. Just don't do things robotically. You need to watch how your pool water is responding and slowly make the changes. If things are not going as planned back off. You are doing a big chemistry experiment and every mix is slightly different.



Bronze Supporter
Mar 27, 2019
I deal with iron stains every year and while there are many different chemicals/materials you can use, I have always noticed the most improvement by doing a major water exchange immediately after AA treatment. I would assume the water in St Louis is pretty cheap, correct? I could spend $400 a year on chemicals to mitigate staining or I can spend $150 to replace my water. I have used the C-u-lator packs before and currently have polyfil in my skimmer to help prevent stains from coming back.

Your point about the stains appearing first on your steps is no surprise and this is where I see them return first. The fiberglass steps have a textured surface which makes it easier for the iron to precipitate there.