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Thread: Iron Stains (I think) Removed - Sequestrant Needed Now?

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    sfbayjay's Avatar
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    Iron Stains (I think) Removed - Sequestrant Needed Now?

    Yesterday I did a drain/refill of my plaster-lined pool to reduce high CYA and CH levels. Wrote about that in another thread here: Refilling now - next steps?

    Due to high CYA, I have been running pool at high chlorine levels for a couple of months, between 13 and 16 ppm, since taking ownership of the house/pool. During that time, I had developed some nasty orange/brown staining on the walls and steps. The stains didn't respond at all to a trichlor tab, so not algae. They also didn't really respond to manual brushing.

    Yesterday, when the pool was draining, I crushed up a vitamin C tablet and brushed it on one of the stains on the steps and, like magic, the stain absolutely vanished.

    I had a LONG time to sit and watch the pool drain, so I figured hey, why not scrub down the walls and floor of the pool with a dilute vitamin C solution and see what happens? Amazing results. Basically I crushed up a handful of vitamin C tablets, maybe 10 or so, then added about a cup or so of water. Using a small scrub-brush, I slowly and methodically applied this liquid to every square inch of the pool that was above-water. Didnít brush hard, just spread the stuff around and then let it sit for a few minutes before rinsing off with clean water from the hose.

    This was miraculous! All the stains were just gone. Amazing.

    At this point, after some reading here, I am guessing the stains were iron deposits, maybe due to extended period of high FC (due to high CYA) and a period where pH was probably too high, as it was hard to monitor pH with FC hovering around 15 ppm.

    Anyway, today, on refilling the pool, the water had a slight greenish tinge to it. In my other thread, Richard320 guessed that maybe it was iron in solution and that the orange iron was causing a green cast to the water. At this point, Iím pretty sure heís right.

    Iíve been running my skimmer with a sock, and after about 3 hours of circulating the greenish water, the sock was stained orange Ė probably iron bits in solution getting strained out? The pool is clearing, slowly.

    BUT, my FC is only at 3 ppm for now. CYA is probably very low, as I removed and replaced about 95% of my water with city water, so Iím guessing CYA is around 10 or so.

    I want to add some chlorine, just to keep algae at bay since CYA is low and it is hot an sunny, BUT Ė Iíve been reading that adding a slug of chlorine to a pool with iron in it can cause all the staining to recur Ė the LAST thing I want since I spent several hours working the stains off the walls yesterday.

    So, do I need to add some kind of sequestrant to keep the iron in solution, before I add chlorine? I donít know anything about this Ė any insights would be so much appreciated. Iíll attach some photos if I can figure out how.

    Photos:
    1. Scrub in progress with Vit-C. Left side of steps done, wall at right done, remainder untouched:


    2. Vit-C Scrub in Progress, lower portion at waterline untouched, upper wall complete:


    Photo 3: Water after refill, green-ish tinted water


    Photo #4: Orange stuff in skimmer sock after 3+ hours of regular pumping/filtering
    Pool: 12,000-gal IG Diamond-Brite, Test Kit: Taylor K-2006
    Filter: Pentair FNS Plus Fiberglass DE FNSP 36
    Pump: Sta-Rite SuperMax HP Single-Speed, 1 HP
    Skimmer: Pentair Pac-Fab "SkimClean"

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    Re: Iron Stains (I think) Removed - Sequestrant Needed Now?

    layer a bunch of paper towels in the skimmer basket and let the pump run. If the towels turn orange/brown, they're grabbing the iron. Check out A Tale of Two Filters... and Ugly, Rusty Water.

    Or add a sequestrant. Jack's Magic is the brand you want to look for.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

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    Re: Iron Stains (I think) Removed - Sequestrant Needed Now?

    OK - paper towels added to skimmer, although skimmer sock was already showing some "catch" of iron I think?

    Can I add chlorine at this time without risking iron precip or re-staining the walls? Just checked and pH is holding pretty steady - now at 7.2 up from 7.1 several hours ago.

    About to run a sample of water up to local pool guy (not a pool store) for him to test for metals (iron and copper). Maybe based on his results a sequestrant might not be a bad idea.
    Pool: 12,000-gal IG Diamond-Brite, Test Kit: Taylor K-2006
    Filter: Pentair FNS Plus Fiberglass DE FNSP 36
    Pump: Sta-Rite SuperMax HP Single-Speed, 1 HP
    Skimmer: Pentair Pac-Fab "SkimClean"

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    sfbayjay's Avatar
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    Re: Iron Stains (I think) Removed - Sequestrant Needed Now?

    Well, testing for metals came back with 0 PPM for both iron and copper. Not sure exactly what to make of that since the paper towels I added to the skimmer are indeed turning slightly orange already after only about an hour. There must be some iron in there, right?

    Maybe I will hold off adding any additional chemicals like sequestering agent.

    But I'm still concerned about whether adding chlorine this evening will cause more iron to precipitate? Not sure what to do here.
    Pool: 12,000-gal IG Diamond-Brite, Test Kit: Taylor K-2006
    Filter: Pentair FNS Plus Fiberglass DE FNSP 36
    Pump: Sta-Rite SuperMax HP Single-Speed, 1 HP
    Skimmer: Pentair Pac-Fab "SkimClean"

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    Re: Iron Stains (I think) Removed - Sequestrant Needed Now?

    Adding chlorine may cause the iron to precipitate but often when that happens it makes it easier to filter it out of the water with paper towels or polyfil. Iron testing isn't all that reliable, if the iron is in a stain, sequestered or precipitated then it might no show up on a test.
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    Re: Iron Stains (I think) Removed - Sequestrant Needed Now?

    Thanks for the advice re. adding chlorine. I went ahead and dosed up to hit FC of 5 and I didn't see much of an effect on the water (no additional rusty haze). However, I then did a thorough brushing of the pool walls and floor which kicked up enough fine sediment to turn the whole pool cloudy for a few hours. Planning to run the filter overnight and then vacuum anything that settles out in the morning.

    One bummer discovery just now: my DE filter pressure has jumped from 12 psi, where it has been sitting since I disassembled and cleaned it a couple of weeks ago, to 17 psi, all since this morning. Maybe I'll have to clean it out again later this weekend l - might not be bad to get any accumulated iron out of the system altogether.

    As always, thoughts or advice welcome. Certainly swimming in uncharted waters (for me) with all of this.
    Pool: 12,000-gal IG Diamond-Brite, Test Kit: Taylor K-2006
    Filter: Pentair FNS Plus Fiberglass DE FNSP 36
    Pump: Sta-Rite SuperMax HP Single-Speed, 1 HP
    Skimmer: Pentair Pac-Fab "SkimClean"

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    Re: Iron Stains (I think) Removed - Sequestrant Needed Now?

    Thanks for the continued help! Things are looking a better today. I vacuumed this morning and most of the green tinge is gone, though I'm still collecting some orange gook on the paper towels in my skimmer.




    Water balance is pretty good, although I know I still need to add CYA since it's near zero.

    Last tests:
    FC 1.5
    CC 0
    pH 7.4
    TA 190
    CH 225
    CYA 0 (probably close to zero, though maybe more like 10 ppm)
    Temp 80

    After this test I dosed with MA to get back to pH 7.2, then about 30 mins later added chlorine to get up to 5 ppm.

    Filter pressure has really jumped - up to 18 psi now. I know "clean" filter pressure is 12 psi since I just tore it apart, cleaned the grids, and replaced DE about 2 weeks ago.

    So, I think I read somewhere here on TFP that once you add CYA that you don't want to backwash or clean your DE filter for awhile, maybe several days? So I'm thinking to clean out the filter again tomorrow morning and then start adding CYA. That will give another 12 - 16 hours of filtering to get rid of more orange (iron?) stuff, then I'll just clean out the filter and get everything OUT of the system. Start with fresh DE and then slowly dose up CYA until I get into a good range.

    Comments on this plan welcome! Planning to use granular CYA and put it in a sock in front of a return jet. Will add a little at a time as I definitely don't want to overshoot. I'd like to end up around 50 ppm, I think, due to Florida sunshine.
    Pool: 12,000-gal IG Diamond-Brite, Test Kit: Taylor K-2006
    Filter: Pentair FNS Plus Fiberglass DE FNSP 36
    Pump: Sta-Rite SuperMax HP Single-Speed, 1 HP
    Skimmer: Pentair Pac-Fab "SkimClean"

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    Re: Iron Stains (I think) Removed - Sequestrant Needed Now?

    The no backwash-after-adding-CYA only applies if you blindly followed the directions on the bottle to pour it down the skimmer. If you follow our suggestion and use a sock, the garnules won;t be in the filter to get backwashed away.

    You're waaaaay overdue to backwash and recharge. If clean is 12 psi, you should have backwashed at 15 psi
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

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    sfbayjay's Avatar
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    Re: Iron Stains (I think) Removed - Sequestrant Needed Now?

    Yeah I know the pressure jumped from 12 to 18 just yesterday. It climbed abruptly once I turned the pump back on, which was right after I finished refilling the pool. Before I drained/refilled, it was chugging along at 12 for 2.5 weeks after I cleaned the filter, then just skyrocketed in the last 30 hours. I'm going to clean it out tomorrow morning and recharge with fresh DE.

    EDIT: I'm planning to remove the grids and flush out all of the DE, not just backwash. I want to remove as much of the iron/orange stuff from the system as I can, and it only takes me about 90 mins to take the whole filter apart, clean the grids with the hose, and put everything back together.

    I'll still probably wait to add the CYA until after I'm done with the filter cleanout, but I really appreciate the clarification - I'm planning to use the sock/return method, but I can see where you'd flush everything out by mistake if you dumped it in the skimmer.

    Thanks again for all the help!
    Pool: 12,000-gal IG Diamond-Brite, Test Kit: Taylor K-2006
    Filter: Pentair FNS Plus Fiberglass DE FNSP 36
    Pump: Sta-Rite SuperMax HP Single-Speed, 1 HP
    Skimmer: Pentair Pac-Fab "SkimClean"

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    Re: Iron Stains (I think) Removed - Sequestrant Needed Now?

    If PoolMath is telling me to add 32 ounces by weight or 33 ounces by volume of stabilizer, that means 2 pounds or just over 4 cups of DRY CYA, right? I just want to be super sure since high CYA was the root of all my drain/refill shenanigans this week.

    All I know at the moment is that my CYA is less than 30 ppm, but I have some strong data and dilution information from how much new water I added, so I'm assuming my CYA is presently around 10 ppm. I'm planning to add another 20 ppm to start. If my assumption about current level is wrong on the low side, then I'll still be too low and I can always add some more. If I'm wrong on the high side, then I'll end up somewhere between 30 and 50, maybe just right. I want to sneak up on a good value rather than jump straight to it, just to limit risk of overshooting.
    Pool: 12,000-gal IG Diamond-Brite, Test Kit: Taylor K-2006
    Filter: Pentair FNS Plus Fiberglass DE FNSP 36
    Pump: Sta-Rite SuperMax HP Single-Speed, 1 HP
    Skimmer: Pentair Pac-Fab "SkimClean"

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    Richard320's Avatar
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    Re: Iron Stains (I think) Removed - Sequestrant Needed Now?

    Yes, granular CYA is what poolmath uses, unless you choose the liquid option
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

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