Help me understand this iron situation.

[TigerGalLE]

So I’ve been struggling with iron staining in my fiber glass pool. I just did an AA treatment with a CUlator in my pump basket. The stains lifted beautifully and my water is balanced nicely now. I had ordered an iron tester and it came today. Iron level in pool water is 0.00. Iron level in my fill water is 0.08. So I guess my iron is coming from my fill water. We have city water. But where did the iron in my pool go? The CUlator has no color to it. So it doesn’t seem to have gone there. I did not add a sequestering agent yet. We had a party yesterday and I didn’t want cloudy water. Last time I added Metal Magic after my AA and had cloudy water for 2 weeks. Staining still came back.

I’m just trying to figure out where the iron went. Should I get an iron filter to put in my hose to prevent the iron from building up in my pool?

The iron tester I got is from Milwaukee instruments.

 

[Texas Splash]

I have no experience with that iron tester. It is safe to say that since you lifted iron stains with an AA treatment, the iron is in a suspended state. It's my understanding that chlorine can influence iron readings, so perhaps either one of those (or both) is why you are seeing odd results. At this point, the water may not be saturated with enough iron particles to filter. We often see owners use polyfill to try and capture iron in the skimmer or though a 5-gal bucket. You can try that, but at this point you might not get much. The best iron trapping seems to be when the water is changing color either from exceptionally high iron content, or high levels of FC and/or pH.

 

[Apsuhead]

I’m in the same boat with our new fiberglass pool. I have AA, Polyquat 60, and Metal Magic ready to go. I’m going to wait until fall to treat the water. My pool water is at 91 degrees with the hot weather lately. I’m going to try the polyfil in the skimmer when I treat it. Good luck!

 

[YippeeSkippy]

If you add a bunch of FC or let your pH go high, the iron should fall out of solution and you can capture a great deal of it in polyfil placed in the skimmers or a bucket device.
IMO, taking the iron out this way is preferable to adding a sequestrant or AA all the time. Out and Gone!

Maddie

 

[TigerGalLE]

If you add a bunch of FC or let your pH go high, the iron should fall out of solution and you can capture a great deal of it in polyfil placed in the skimmers or a bucket device.
IMO, taking the iron out this way is preferable to adding a sequestrant or AA all the time. Out and Gone!

Maddie

Maddie,
Do I just put the poly fill in the skimmer? Do I need a skimmer sock or anything?

 

[Texas Splash]

Do I just put the poly fill in the skimmer? Do I need a skimmer sock or anything?

You can do it either way. Some people get concerned about the poly trying to slip through the basket, but you can experiment with either method based on your water flow.

 

[TigerGalLE]

So now my pool is green. I’m SLAMing because what else can one do? The water is cloudy and has a green tint. I’m assuming this is algae but could it be iron? I just retested the iron in my water and it read 0.75. Polyfil comes today and I’m going to put it in the skimmer.

 

[Texas Splash]

Please post a pic of your water.

 

[TigerGalLE]

Hard to see the green tint in the picture.

 

[TigerGalLE]

Also I tested the iron level again with this tester and it said 0.00ppm. So I don’t know. The iron must be moving in and out of some kind of state. Or this machine is wrong. Or I’m using it wrong.

 

[Texas Splash]

You definitely have algae. Your Poolmath logs haven't been updated since last week, so I don't know what your current levels are, but if your CYA is still 40, your FC should be 16 per the FC/CYA Levels. Your pH should've been lowered to about 7.2 before increasing the FC to that elevated SLAM level. Maintaining the SLAM and passing all 3 criteria is always a priority before treating for iron chemically. But during the SLAM Process process is the perfect time to use the polyfill, so as soon as you receive it, incorporate it into your filtering. Try the skimmer, and if you have a separate submersible pump, circulate some water through a 5-gallon bucket. During the SLAM the elevated FC level should help to filter iron. But you have to follow-through with the SLAM to remove the algae.

 

[TigerGalLE]

------------------------------------------
Test Results 08-05-2021 @ 11:04 AM
------------------------------------------
Free Chlorine: 15.5
Combined Chlorine: 0.0
pH: 7.5
Total Alkalinity: 70
CYA: 30
Salt: 3000
CSI: -0.31

 

[Texas Splash]

Very good. Then an FC of 12 should be enough to proceed with the SLAM. From the pool pics, you don't appear to have anything that could hide algae unless your pool has a large light fixture with a niche behind it. Other possibilities include under a drain cover and in/around the skimmer and weir door (flap). Even though your robot should be doing a fine job on the majority of your surfaces, continue to brush those areas it can't reach. Biofilm on each surface needs to be exposed for the chlorine to penetrate.

What type of filter do you have? I don't see it in your signature.

Also keep in mind that iron testing can be influenced by chlorine, so that could be a reason why your iron testing seems inconsistent.

 

[TigerGalLE]

Thank you. I have a sand filter. I’ll brush brush brush. FC is already down to 12.5 so it must be working. I was worried I had Iron bacteria but that doesn’t seem to be the case. I hope.

 

[TigerGalLE]

How often should I backwash during this process? Just when my pressure jumps?

 

[Texas Splash]

We backwash generally when the pressure increases by about 25%. So next time you do backwash, make note of the new clean (starting) pressure and watch for that 25% increase.

 

[TigerGalLE]

Ok my water is clear. I lost 1ppm of chlorine last night. I turned my SWG back on and am hoping I’m done with the algae. My CYA is 30 and I lost 6ppm chlorine yesterday without adding any and without the SWG on. I work 12 hr shifts so I wasn’t home and it was very sunny and hot. Should I increase my CYA now that I’m done with the SLAM? I have liquid conditioner I can add. I still have mild stains but the polyfil has collected a lot of brown stuff. So I’m optimistic I removed some iron at least.

 

[wireform]

No, do not increase the cya yet .Please give it one more day of slam as per the given cya you have along with another OCLT for EXTRA INSURANCE. Better be safe then sorry as you may be skirting the fence on the overnight loss and in due time can be back to square one. We've see this scenario time and again.

 

[TigerGalLE]

My pool is looking good. I think staining is improved and polyfil is collecting iron. I found algae in the sealant around my skimmer so I sprayed with bleach, scrubbed and brought my FC back to 12. My numbers are up to date on pool math.

 

[Texas Splash]

Looks outstanding!