Iron stains AA plus Metal Magic?

[JoyfulNoise]

I’ll keep it simple (I’m mobile at the moment and it’s hard to drive and explain chemistry at the same time).

AA is a reducing agent. It “reduces” iron 3+ ions (insoluble at near neutral pH) to iron 2+ ions (highly soluble at near neutral pH). Most stains on pool surfaces are iron (III) compounds (oxides and hydroxides). Iron 2+ ions are not stable in highly oxidative solutions (chlorine is an oxidizer) and so they will quickly convert back to iron 3+ ions. However, if you add a sequestering agent (there are many types of these) then the sequestering agent can hold the iron 3+ in solution by binding to it before it can react with oxygen to form scale. Over time chlorine destroys the sequestering agents causing the release of iron back into solution and, ultimately, causing stains. Some sequestering agents are simple phosphate based chemicals that are good at holding iron in solution while other sequestering agents are charged polymeric ions that will capture the iron and can precipitate out of solution as a solid inside the filter (though no guarantee that it will). All sequestering agents are susceptible to chlorine oxidation, some more quickly than others.

The only way to truly eliminate iron staining is to get rid of the source of iron in the fill water used in the pool. Well waters, especially ones from acidic or shallow aquifers, will generally be high in iron content.

 

[setsailsoon]

That sounds like as reasonable an explanation as I have heard. And I would conjecture that pH is the factor that tips it one way or another. The other thing I noticed is the AA instructions on the site say to get your pH down to 7.2 and the instructions for MM say to get your pH above 7.5. How did you reconcile that? because if I understand that wiki correctly when the pH goes back up the AA doesn't do as good a job of holding the Fe ions.

I faced the same dilemma on pH. Went down to about 7.0 accidentally then started AA. A little bit goes a LONG way! After that and after adding the algaecide then waiting for pH to rise I added MM right at 7.5. Iron staining was completely gone way before I added the MM. Pool looked brand new within 30 min of AA. And stayed that way for almost a year.

Chris

 

[mguzzy]

I’ll keep it simple (I’m mobile at the moment and it’s hard to drive and explain chemistry at the same time).

Amazing .. and while you were driving no less.. I might add that it was O-chem that made me realize I would rather major in physics. ..and I too have trouble explaining physics while I am driving, mostly because a chalk board tends to block the windshield.

So, from a practical "pool" standpoint a lower pH environment helps the AA react with Iron to lift the staining. That puts the Iron in solution as an ion, and not bound to the AA in any way. Which allows the sequestering agents to bind with the iron. So once the iron is in solution I can let the pH drift up for the sequestering agent to do its work. right? Metal Magic, it appears is phosphate based (1-Hydroxyethane-1,1-diphosphonic acid according to the SDS). I wonder what the mechanism is that causes it to crystallize and if that is an efficient way to remove the iron or does it only convert some of it? Also, its probably the wrong kind of phosphate compound to be removed with a phosphate remover.

I get that a water exchange is probably the better method to get rid of the iron. I'm thinking that I got mine from contaminated salt since I didn't see any in the pipes before the SWG was put in. And I didn't pay attention to the brand of salt I used until later. I have chatted with my water company, and they don't publish the Iron amounts. So I don't really know what that contribution is. But I already have the ingredients to give it a try so I'm going to do my AA/MM treatment in concert with opening my pool up this spring and we will see.

 

[markayash]

I honestly think my iron is coming from the stone coping. Never had any iron issues until I had the old brick stuff removed and stones added.
My staining was gone until I let my PH jump up to 9ish ( off the chart ) and boom it came back.
I just hate added metal magic or similar all the time.
debating sealing the stone but not sure if that will cause a bigger mess

 

[markayash]

I just did a AA treatment and everytime I am amazed at how the brown stains just vanish! letting the pump run a little longer and about to add my seq agent.
I will also make sure to keep adding seq agent and do netter at watching my PH!!

 

[mguzzy]

I am curious.. what temp is your water at. Mine is still in the low 50's so I am waiting for things to warm to above 60 before I use the MM sequestrant, according to the instructions.

 

[markayash]

Mine is right at 50 also. I figured I wouldn't have to worry about algae as much.

 

[mguzzy]

Yeah I see your point.. but if you are using MM, the bottle says it works best when the pool water is over 60.. Not sure why but that's what it sez

 

[markayash]

I used Jacks magic Purple stuff but didn't think about that.

I am following a process jacks recommend to me once. Add their product that matches your pool, I got purple since it's made for salt..
They also recommended I add their filter fiber to my cartridge filter. Not sure if it helps but then it was rust colored when I cleaned it a couple months later

 

[mguzzy]

If I understand it the filter fiber is the same thing as poly fill that is recommended to put in the skimmer basket.. I'm sure you have read the threads where owners have created a filtering barrel of sorts. could your "rinse" the rust color off the fiber like you can with poly file? I have some AA on order and I plan on doing my treatment just when its warm enough to hit 60 deg. I'm hoping the algae will be held at bay by keeping it as cool as I can.

 

[markayash]

Filter fiber is suppose to make your filter work better. Kind of like adding DE powder. It coats it with a Powderly looking stuff.
I may get some poly fill today and leave in the skimmer.

 

[setsailsoon]

I just added polyfil to the skimmer. Worked fine and was way easier than messing with the filter. Polyfil seems to trap everything and plugs up pretty quickly. My temp was in the 80's.

 

[markayash]

This is my 3rd treatment and not sure why but it seemed to work better then the 1st 2. Not sure if it's the colder water or just getting what iron was left.
It is nice not to have to worry about algae as much while my water is around 50.

 

[borjis]

My water is at 42.
Ive got all the supplies (jack's pink stuff as the sequestrant). Filtering now to get it sparkly clear before i begin. I have very light staining. +1 doing it cold so algae is out of the realm.

 

[markayash]

Mine has been running with the Purple stuff and filter fiber for about a month. Since the flow was down I took them apart and it had a weird Grayish color and it all washed off. Hoping that's Iron I pulled out of the water.. I am going to keep adding Purple stuff monthly and see if the stains stay away!

 

[borjis]

I'm in the last days of the first week in the 2 week wait phase.
Ph 7.2 fc 3.
I cannot believe how blue my liner is!!!
There must have been a light sheen of stain on the entire surface, then 2 areas where it was worse.

I have completely recovered the original medium blue. And here i though for awhile it was sun fading.
Yay!!!
When im done I'll post my notes and what i did on this thread.

 

[markayash]

I'm in the last days of the first week in the 2 week wait phase.
Ph 7.2 fc 3.
I cannot believe how blue my liner is!!!
There must have been a light sheen of stain on the entire surface, then 2 areas where it was worse.

I have completely recovered the original medium blue. And here i though for awhile it was sun fading.
Yay!!!
When im done I'll post my notes and what i did on this thread.

I think doing the treatment in cold weather is the best. Don’t have to worry about algae as bad and it seemed to work better at removing stains for me anyway.

 

[setsailsoon]

Last week I had a pH excursion from neglect on my part recently along with above target on FC and my brown spot in the shallow ledge area came back big time. We planned to put the house on the market so I had to "fix it" quick or my wife was going to call a pool service. I dropped pH down to 7.5 then added Metal Magic hoping it would remove the stain. I added the normal dose for iron removal but put it all in the shallow ledge area over the spot. This improved the stain but it was still pretty visible. So I sprinkled about a half cup of AA right over the stained area. In about 30 min the stain was completely gone and the pool looks great! If I can get some CUlater I'll add it this time and hopefully remove the iron for good. Don't have time to get the cationic resin this time and experiment with that. Dang!

Chris

 

[markayash]

Glad you had extra AA to get it out! Let me know if the Culater works. I debated on getting a couple but heard mixed reviews here.
Also Jacks filter fiber helps. Coats your cartridge filter and makes it a lot more efficient. Guy form jacks Magic recommened it onece.
I only use it when doing a AA treatment

 

[borjis]

I too have been considering an investment to a real good filter for getting the iron out. This liner is going on its 6th season. Like to keep it this way.

Thanks for that story Chris. I'll be watching both ph & chlorine like a hawk to keep it nice.