Featured Iron Removal Experiment

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GaryParr

GaryParr

Well-known member
Aug 21, 2020
158
Rhode Island
Pool Size
19000
Surface
Vinyl
Chlorine
Salt Water Generator
SWG Type
Hayward Aqua Rite (T-9)
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.


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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.
 
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JoyfulNoise said:
... “chemical reactor” ... leak ... damage ... secondary container...
Click to expand...

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.
 
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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.
 
GaryParr said:
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.
Click to expand...

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 said:
6.8 going in, 8ish coming out.
Click to expand...

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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.
 
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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.

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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.
 
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.
 
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GaryParr said:
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.
Click to expand...
If you float it in the pool,
Use of those little mesh laundry bags and encase it so it can’t be hurled out onto the floor of the pool if the container breaks apart.
 
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I just wanted to say, OP, that you are my kind of guy. Curious to see the results!

I also have well water that has tons of iron in it. A few years ago i had an 'iron breaker' installed as part of our water treatment system (we have the well water coming into a pH neutralizer -> iron/sulfur breaker -> water softener -> 5 micron filter) and that seems to work well for getting rid of most iron (last water test i did on our well only had 0.125 ppm of iron).

However, we moved into this house 5 years ago. the pool had been filled for years with the iron-water. So i had a ton of iron deposits all over the liner and fixtures in the pool! I had to do the Vitamin C treatment a couple times a season otherwise it looked dirty.

Keep fighting the good fight, sir!
 
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The results are in, and they are disappointing.

I'm not seeing a lot of iron on that poly-fill.

That was after two solid days of running this contraption with doubled cal-hypo tabs. It seems my soluble iron is being very, very stubborn. But, results are results. I'm left wondering if raising the pool to shock level and then trying this again would have an effect. I may try that at the end of the season, but for now... the kids want to use the pool. So, Jacks Magic Purple Stuff added to encourage the iron to keep being stubborn and all my chemical levels balanced.

The experiment isn't over yet though! I will bring this setup back out of storage the first time I have to top off. Since the well water is the source of my contamination, the iron concentration may just be high enough for this to have some positive effect. I'll come back and update this thread when we reach that stage.
 
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JoyfulNoise said:
Is it just the picture or is that polyfill kind of grey? Was it grey to start with?
Click to expand...

Could be the picture throwing it off a bit. Started as white, but now It's more blue tinged than anything. Seems to me the same color as the cal-hypo tabs. I'm assuming it's from chunks of the tab breaking up and getting washed down the line to get caught in the filter where they were still in the process of dissolving as I shut the experiment down. When I run this again off the well water, I'm going to skimmer sock the tabs in the reaction chamber to prevent that from happening.
 
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