Iron Removal Experiment

[GaryParr]

I'm trying to find a decently cheap way to remove soluble iron from my pool and from my well water that I use to top off with. After some great advice from @JoyfulNoise in this thread I decided to try a variation of the poly-fill bucket contraption.

I'm going on a theory. A very simple "I may not actually understand this" theory, that's based on the following principles:

1. Chlorine reacts with soluble iron and does something indistinguishable from magic that makes the iron get stuck in poly-fill.
2. It takes a hot minute for this reaction to occur.

Assuming any of that is true, my task was to modify the bucket method to have chlorination -> time -> filter. To accomplish this, I added bulkhead fittings to a screw-top water-tight container that's big enough to hold a 70% cal-hypo tab. I use a cover-pump to push water through that container where the water picks up the chlorine. And, since we need to give the chlorine time to find the iron and ask it out to the dance floor, a 50' garden hose separates that chlorination station from the filter. For the filter itself, I had a section of 4" PCV pipe that, at 2' long, seemed "filter shape" and should put more water in contact with more poly-fill than a 5 galon bucket would.

Time will tell if this does anything. I'll report back after that first cal-hypo tablet is used up.

 

[JoyfulNoise]

Interesting setup.

My only comment/concern would be not leaving the “chemical reactor” on the deck like that. Should it leak concentrated cal hypo liquor, you’ll damage the deck. Maybe put it in a secondary container of some kind to avoid spills.

 

[dereksanders]

Ingenious!

 

[Mdragger88]

Looking forward to the results of this experiment !

 

[GaryParr]

... “chemical reactor” ... leak ... damage ... secondary container...

Good call. I could just keep that reaction chamber in the pool itself, but I'm curious to see how well this cheap screw lid thing holds up to being a pressure vessel, so it's now taking up residence in a plastic tub.

 

[Newdude]

 

[GaryParr]

Curious about the actual chlorine concentration, I ran a drop test on the output. It's 6.5 PPM. May not sound like much, but I just finished an AA stain treatment the other day so my input water has 0 PPM. I'm sitting at about 60 for CYA since I haven't brought that up yet to my normal 75. Honestly not sure if that FC level will be enough to force the iron out. Time will tell. The opaque nature of the PVC is seriously testing my patience.

 

[JoyfulNoise]

Curious about the actual chlorine concentration, I ran a drop test on the output. It's 6.5 PPM. May not sound like much, but I just finished an AA stain treatment the other day so my input water has 0 PPM. I'm sitting at about 60 for CYA since I haven't brought that up yet to my normal 75. Honestly not sure if that FC level will be enough to force the iron out. Time will tell. The opaque nature of the PVC is seriously testing my patience.

Test the pH of the output as well. It’s a combination of high pH and FC that drives precipitation. The poly fill simply gives the effluent a lot of surface area to deposit on to.

 

[GaryParr]

6.8 going in, 8ish coming out.

 

[JoyfulNoise]

6.8 going in, 8ish coming out.

 

[JoyfulNoise]

Are you measuring 8 using the phenol red indicator or a pH probe?

You might try adding two cal-hypo pucks to see if you can goose it up higher. And also slow down the pump a little bit.

 

[GaryParr]

Phenol red. I may have a digital probe, need to find it. But, to your point... need to go big or go home. So, shut it down and checked. Poly-fill is clear, no trapped iron. Oh well, not the result I was hoping for, but still a result.

Science!

Threw a second tab in the chamber. I didn't slow the water flow yet since this cover pump already has a low GPM. PH drop test is now a very lovely neon shade of purple. For chlorine, I lost count somewhere north of 50 in the drop test, so > 25 ppm.

 

[JoyfulNoise]

The precipitation process can take a while. If the amount of iron is minimal, it's not always easy to get it to precipitate out. People that get the really brown nasty looking polypill typically have A LOT of iron in their water. You might just let it run for a few days and see if anything shows up. I doubt the cover pump uses much energy.

Also, with the FC now a lot higher, the phenol red drops won't work because the chlorine interferes with the color change. The only way to get a reliable reading at high pH is to use a probe.

 

[GaryParr]

Understood.

I don't believe my iron level is all that high. It took a couple years for the staining to become noticeable, and from there it just darkened slowly over time. When I closed this past winter, I raised the chlorine pretty high. Not sure how high, but after I opened this spring and topped off it was sitting at 8 ppm. The stains were very apparent. The AA treatment made everything look new again. I had forgotten how white my stairs are supposed to be!

Anyway, I'm aware this may not work. Or, may work but not be practical. Just wanted to find out for sure before I resign myself to a life of sequestering agents and occasional water swaps.