(Iron) Discoloration Under Waterline in Fiberglass Pool - AA treament, Polyfil, etc

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Apsuhead

Apsuhead

Bronze Supporter
Apr 27, 2020
501
Clarksville TN
Pool Size
19250
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Hayward Aqua Rite (T-9)
My fiberglass pool is starting to get a tan/brownish color all the way around under the waterline. My pool math numbers have been pretty consistent since install last December. Any ideas?
8B068B51-AAD2-424B-AA28-3B90874DE71F.jpeg
 
Try rubbing a slurry of vitamin C on it. If the brown comes off then it is iron staining in your pool.

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@Texas Splash may have thoughts.
 
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Hard to tell from the pic, but perhaps you might have a tiny scum line developing as well. Does it feel sticky at all? You can try the Vitamin C rubbing test as Allen noted (iron). If that doesn't work, try gently rubbing a Magic Eraser on it. Let us know if either of those work for you.
 
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I will get some Vitamin C to rub on it, thanks. I went around and cleaned the waterline with a magic eraser and it didn’t do anything to the discoloration under the waterline. It isn’t sticky. Here are my test results from this morning and some pics. It is just slightly noticeable when the water is wavy. I’ve got my Hayward T-9 SWG set at 35%. Thanks!
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Crushed some vitamin c tablets in a sock and rubbed the stain. Came right off. I rubbed half of the entire top step in this pic (towards top of pic) and you can see the difference.
032B3574-0A8D-43BB-82F5-48877B126581.jpeg


Please advise on next steps. Trying to study ascorbic acid, lowing PH, polyquat, DIY bucket pillow filters, etc.

Not sure how iron got in pool but I did put a lot of lime and fertilizer around the pool area when working on the lawn in the spring.
 
You can do a full AA treatment of your pool following the Ascorbic Acid Treatment - Further Reading or just scrub sections of your pool with vitamin C.

But with iron in your water the iron will redeposit on the pool surface unless you continuously add sequestrant or drain the pool and refill with iron free water or can successfully filter out the iron using polyfill.
 
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@Texas Splash I ordered 3 lbs of ascorbic acid. How much Polyquat 60 & Proteam Metal Magic do I need to order? I guess I’ll try putting some polyfil in the skimmer to try to get some iron out afterwards. I went out to the pool at sunset yesterday and I could really tell where I had rubbed the vitamin C, it was very surprising to be able to see the staining compared to the clean spots. Thanks for all the help!!!
 
Good to know the Vitamin C confirmed your suspicions about iron. I don't recall, but the bottle of Poly and Metal Magic should say how much to use based on gallon size of pool (i.e. x-amount per 10,000 gallons). So I would just follow those instructions. Good luck!

Ascorbic Acid Treatment - Further Reading

www.troublefreepool.com www.troublefreepool.com
 
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I just ordered the MetalMagic and Polyquat 60. I wonder how long it will take my FC to drift down to 0? It will be near 100 and sunny the next few days 🥵
 
Apsuhead said:
I wonder how long it will take my FC to drift down to 0?
Click to expand...
Not long with an SWG turned off. For what it's worth, some owners wait until just before winter closing with cold water (below 60F) to do an AA simply to help avoid an algae issue.
 
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Do you have red clay where you live? A good part of the south has red clay due to a high amount of iron in the soil. My pool gets stains like that and I just clean them off with vitamin C when needed and call it a day. As long as it’s not coating the entire pool I am not going to worry much about it.
 
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Apsuhead said:
Yes. My whole back yard was red clay when they installed the pool last winter.
View attachment 359290
Click to expand...
Yep that’s like our clay here. Your going to get iron in the pool and get some staining. Even if you treat it, you will get more. That’s why I’m just going to spot treat unless it gets super horrible.
 
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My dog was in the pool today and then ran around the lawn and got dirty feet. He later got back in the pool and the red clay from his feet covered the pool steps. I’m sure that’s where a lot of it is coming from 😬
 
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Update - I’ve had my SWG turned off for a week trying to get my chlorine to drift down. My pool water is down to 59 degrees. Hoping I can try the AA treatment soon and filter the iron out with polyfil in the skimmer.
 
Still waiting on my FC to drop. It’s still at 4.5 and i’m running out of time before the cold weather gets here. I leave my pool uncovered in the winter but I still plan to blow out the lines and winterize. 🥶
 
I went ahead and cleaned my fiberglass pool good this morning then added 3 lbs of ascorbic acid with the filter on recirculate for about an hour. Almost all the iron staining disappeared. I then added 2 bottles of proteam metal magic. I put polyfil in the skimmer and put filter back on filter. We have some cold weather with lows in the teens coming so I wanted to do this treatment now so I can blow out my lines and winterize before winter weather arrives. Thanks
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I went out and cleaned a few leaves out of the pool this morning. The water has gotten a little cloudy but still looks great. I turned up the pump speed and added more polyfil to the skimmer. I partly closed the lines from the main drains to pull mostly from the skimmer. Anything else I should be doing? Thanks!
 
I just tested my water and the PH was around 7.0 and chlorine was near zero. I added some PH increaser and liquid chlorine. I have some AA still on the bottom of the pool so I ran my robot and still have polyfil in the skimmer. Hopefully as I start to balance the water, the polyfil will catch some iron.
 

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