What I thought was old iron stains on my cartridge filters, is still iron in the water!

mguzzy

Gold Supporter
Jul 8, 2015
2,386
OV, CA
Hi all
Amazingly I found no posts on the forum about this. So I was the victim of the dreaded Iron contaminated Clorox Pool Salt about 3 seasons ago. Apparently it was worse than I thought. There is a nice darker area in my mottled dark plaster in the deep end from salt additions from that year. But I think the winter rain dilutions have gotten it mostly out of the pool But I am left with stained cartridge filters. I have done a TSP soak followed by an acid soak (per chemgeeks instructions). The stains are still there. I know its Iron because if I sprinkle some ascorbic acid on it they stains go away. Does the staining affect the filtration and I can just ignore it? or should I perform a ascorbic acid bath next?

Thanks all.
 

mguzzy

Gold Supporter
Jul 8, 2015
2,386
OV, CA
Ok.. I was not particularly worried that the iron stains would go back into the water.. I more wondered if the stains affected the filtration of the cartridges. I have since given them a thorough cleaning with TSP, followed by acid washing and though they are whiter, the stains are still there in the form of brown spots. They are back in service and seem to doing well.
 

mguzzy

Gold Supporter
Jul 8, 2015
2,386
OV, CA
It can't hurt to give the cartridges an AA bath the next time you have them out for cleaning.
Yeah I considered that...and I think I will. I noticed the stains could be taken off the filters with a sprinkle or "Fruit Fresh" which is essentially powdered AA.
 

mguzzy

Gold Supporter
Jul 8, 2015
2,386
OV, CA
I've retitled this thread and perhaps the mods can move it to a more appropriate forum (@Leebo ) Probably one of the Water Chem forums...[Edit:thanks]

It appears I have a continuing iron problem.. Apparently the winter rains didn't get it out and it only got bound to something in the water. One never expects to deal with the iron thingy until it happens.

So since putting the filters back in service I also added a some MA to bring the TA down a bit while also doing the SWG/pH dance. Well, the next day the pool turned a nice emerald green. Its still TFP clear, just a nice shade of Creme de Menthe. Obviously the iron came out of solution and oxidized. Was it the addition of the MA, or residual chems from the TSP bath and acid wash? Whatever happened it coaxed the iron to show itself. Right now, I have a polyfill filter running in my skimmer basket that I made from the guts of 10,000 stuffed animals that were ripped up by the dogs. whoo hoo.

This mornings readings: pH 7.5 (stable for the last 4 days since the MA addition), Alk 110 (and stable), FC 5 (OTO), CYA 70ish, Water temp 73. The pool this morning was an enticing emerald green..a dash less than yesterday.
20200625_082226_sm.jpg
No, that's not the color of my plaster. If you notice the spa is less green, the valves are in spillover mode so it gets only the filtered water. The stuffed animal guts iron filter is working as it should! Before the morning rinse, the bucket has last nights rinse water
20200625_071820[1].jpg
I put a nylon sock on the basket over the top of the stuffed animal guts filter. Otherwise I get a billion leaves in the fibers and its a pain to pick them out. After the morning rinse, the bucket now has last nights and this mornings rinse water
20200625_072213[1].jpg
I'm hoping the iron will stay oxidized long enough for me to filter it out. I'm guessing if the pH changes it will become insoluble again and go back into solution.

My son didn't believe any of this hocus pocus. He just saw green and started screaming "DAD! there's algae in the pool!" Which of course started an argument as to why the pool was green. So after I showed him the way the polyfill filter worked and explained the iron chemistry thing, he sez.. "Why didn't they teach us something cool like this in high school chemistry!"
 
Last edited:

Spitdog

Member
Apr 17, 2019
24
North East
My town has high iron in the water supply. When we had our liner replaced and refilled the pool. You couldn’t even see the drain in the deep end because the water was so clouded by the iron.

I took a cheap pillow that has that Polly filling and pulled it out of the pillow and stuffed it in both skimmers.

I turned off the main drain and let the pump run all night. In the morning , both skimmers were dark orange with the collected iron. It took awhile but if finally cleared up. That pillow trick worked good.
 

mguzzy

Gold Supporter
Jul 8, 2015
2,386
OV, CA
Update. I filtered all day yesterday and through the night. I rinsed the polyfill this morning and it was noticeably cleaner. So was the pool. By afternoon it is catching much less iron and the pool is back to looking TFP clear. So either I have filtered about all I'm going to get or the iron has snuck back into solution. I'm going to leave the stuffed animal guts in the filter through the weekend to see if it filters anything else, and I'm going to put the filter back on its regular schedule. I didn't know if this process was going to take a week or what.. so it really only took a few days.
 
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