Recurring Iron Stain -- Looking for permanent solution

[Lunarlight]

Hi,

I recently (3 years ago) bought a new house with a 16x25 fiberglass pool (10 000 gallons) and I am having recurring Iron Stains issue which comes back at least once or twice every season. It covers the entire submerged fiberglass which becomes yellowish.

Before I start my acid ascorbic treatment:

FC: 0 (I did let it go to for the ascorbic treatment, previously was 4-6)
CH: 400
TA: 80
PH: 7.2
CYA: 50

I followed the directions as per the following link: Ascorbic Acid Treatment - Further Reading

Filter on recirculate, about 1 pound of ascorbic acid, add enough sequestering agent, etc.

Within minutes, all stains are gone and submerged fiberglass is pristine white... YAY! After 24-48 hours, I balance water again with PH between 6.8 and 7.2 and start pouring liquid chlorine VERY SLOW until all of it is eaten by the ascorbic acid... After my first poured gallon of liquid chlorine, I slowly saw a few stains come back... i continued to pour liquid chlorine very slow (half a gallon and then wait 30 minutes and check for FC... Result is always 0... continue to pour.... but after 3-4 gallons, FC was still 0 but ALL stains are back covering the entire pool..

I am getting very discouraged and I do not know what to do next.. I live in the city, I don't believe water has that much iron in it. I have a 2019 Hayward heat pump and a very old pool pump that I believe is rusted.. I had to get it repaired two years ago and I remember it was pretty rusty.. Could my water pump be the cultpit ?

I just do not know what to do anymore and before I start the process again, I was hoping you fine folks can provide some guidance on how to permanently resolve my issue.

If you are still reading, thank you VERY VERY much!

Peter

Hi Peter, your issues read like the ones we’ve been having this year. The culprit for the iron for us is the sand in our brand new sand filter. Talk about feeling duped by the pool guy when we asked for a replacement to our DE filter and he was insistent on a sand filter. At the very least, we regret not going with glass beads. We’ve lost two months to iron stains, cloudy water, and the time consuming cycle of managing chlorine and PH for this metal removal process. Still love the pool even after 9 years but wanting to pull my hair out! Good luck to you too.

 

[revitup]

We went through three complete water exchanges chasing an iron staining problem. After eliminating all other possible sources for the iron, we determined that it had to be coming from the salt. Bit the bullet and used Aquasalt this last time and so far no more staining.

 

[Hoster]

We went through three complete water exchanges chasing an iron staining problem. After eliminating all other possible sources for the iron, we determined that it had to be coming from the salt. Bit the bullet and used Aquasalt this last time and so far no more staining.

This is an excellent point. I am having issues (last 2-3 season) with rusty water and been dumping ascorbic acid like crazy (every 2-3 days). Repaired the rusting wall inside the liner last season but this season is worse. Been using Morton's or Clorox salt over the years, and didn't know about Aquasalt (which seems to cost over $40 a bag vs. 8 bucks). In a long run, cheaper than paying $300 bucks for a 55lb box of ascorbic acid.

 

[SpykeYs]

D

This is something you'll have to gauge as each pool and AA transition is a bit different. Once you get the pH back to a safe level, you'll add (for example) 1-2 ppm worth of chlorine and watch to see if staining tries to return. At the same time, you'll test the FC often since you can expect the residual AA to use some of the chlorine. At some point, as you add fresh chlorine, it should consume the residual AA and begin to hold. Your FC may also be fighting the sun's UV, so it's all a balancing act. You'll have to babysit the pool today as you add chlorine & re-test to see if it's holding. At the same time, keeping your fingers crossed the stains don't try to come back.

Ascorbic Acid Treatment - Further Reading

www.troublefreepool.com

Good morning Texas Splash -- I wanted to give you a quick update.

My pool has never been so white! The AA treatment was definitely successful this time around and my FC is now holding fine. I will continue to test throughout the day to confirm and better understand how to adjust my Hayward Aquarite. I currently have the dial at 35%.

Pool results:

Fiberglass: White with no stains
Water: Clear
FC: 7
CH: 425
TA: 80
PH: 6.8
CYA: 60


I think most of my values are fine. I will look at moving my CYA to 70-80 but as I added the stabilizer yesterday, I want to give myself 5-7 days before retesting. What about my PH ? I have already brought my TA to 80 which had some effect on PH but it is still a bit low. Do you suggest I leave at 6.8 and retest daily or should I bring it up to 7.2 now ?

Thanks again !!! You have been very helpful. Now I just need to figure out what brings the iron in the pool. I have 3 potentials leads.

1. Pool Pump is 8 years old and pretty rusted on the outside...
2. I changed the sand in my filter with new sand about 3 years ago and I do see a relationship with the stains as they have been very strong in the last 3 years.
3. I have stamped concrete all around the pool. I know there is A LOT of iron rods in the concrete.... Wondering if this could the the cultpit when the snow is melting and going into the pool...

Thoughts ?

 

[Texas Splash]

Do you suggest I leave at 6.8 and retest daily or should I bring it up to 7.2 now ?

6,8 is too low. Do what you need to so it can get back into the 7 range. A little higher TA and/or aeration to help should work.

 

[Texas Splash]

Not sure about the iron. The pump rust is external so nothing from in the motor should be getting into the water. I've not heard of sand being a contributor either. Rebar in the concrete could potentially stain the concrete itself if the rebar was too close to the surface, but should not impact the pool. I don't recall, were you ever able to confirm with your local city/county authorities about iron in the local water? Ever able to obtain an annual water report?

 

[Bperry]

Hi Peter, your issues read like the ones we’ve been having this year. The culprit for the iron for us is the sand in our brand new sand filter. Talk about feeling duped by the pool guy when we asked for a replacement to our DE filter and he was insistent on a sand filter. At the very least, we regret not going with glass beads. We’ve lost two months to iron stains, cloudy water, and the time consuming cycle of managing chlorine and PH for this metal removal process. Still love the pool even after 9 years but wanting to pull my hair out! Good luck to you too.

Separate thread but If you used pool filter sand then the iron wasn’t from the filter. The glass media doesn’t work any better than regular pool filter sand. The only way to remove metals is to replace the water.