Crazy Stain Problem!

zgsteele

New member
Aug 12, 2020
2
albany ny
This started about a 1.5 months ago. Literally woke up to pool having green/brown tint. It worsened (was a spotty stain at first, then everywhere after 24hrs, then stabilized (no worse or better in appearance). It looked like entire liner and stair had stain. I took sample and all conditions were normal with no iron or copper showing. I took vitamin c pill and it immediately went away where I touched it to surface. I also tried citric acid and chlorine tablet but they did nothing. I did research about rust and assumed this was my problem. I noticed a little rust on my ladder so I just removed it. I dropped chlorine to <1, added 2 cans of stain-free and pool was normal again in no more than 1 hr! I then added 2 containers of metal-free, filtered for 3 days, backwashed and rinsed sand filter, then start slowing turning up chlorine on generator. After 1 week stain reappeared and looked the exact same as before (not worse or better)

I repeated this all a 2nd time (only difference is I added only 1 container of stain-free and 3 containers of metal-free) and again pool was blue but in 1 week stain returned (looked exact same – not worse or better).

I then did treatment again (1 can of stain free but tried different chelating agent - dont remember the brand). I also added culators in my skimmer. I kept chlorine at zero for 6 days and backwashed filter for 5mins and rinsed for 2 mins each day (adding back fresh water when low). On 6th day, I started chlorine generator and 7th day stain was back in full effect. I shocked it to get chlorine back up (it was still <1 when stain reappeared), added 1 container of stain-free (with chlorine levels normal) and pool went back to normal blue color. I took sample to store and results were all normal. I also cut open the culator and it was white (after 2 weeks). The pool is still blue this morning (3 days with normal chlorine levels after adding the container of stain-free), but I’m expecting that by this weekend stain will return for 4th time.

I’m at a loss for what to try next – any suggestions? I’ve never experienced this issue before. I really appreciate you guys

38,000gal salt pool
Installed 2012
Pentair 400 heater
Sand filter – I changed sand for Zeosand back in May
Hayward T15 turbocell (replaced cell in 2019)

Pictures:

1 – color when stain appears
2 – same as 1 but showing different angle so you can see landscaping around pool
3 – sprinkle a little stain-free to show stain immediately disappear
4 – 12hrs after adding stain-free (sprinkled 1 can around edges, circulated 4 hrs, then let sit overnight). I’d say this is what my pool normally looks like
5 – picture of deep end before adding stain-free (a little cloudy but I think because chlorine was 0 for 6 days)
 

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I took sample and all conditions were normal with no iron or copper showing. I took vitamin c pill and it immediately went away where I touched it to surface.
Congratulations! You have iron. :) Welcome to TFP! :wave: Regardless of what the store testing is showing, and believe me pool store testing is often flawed, the chemical reaction doesn't lie. Vitamin C remove iron stains, so you already confirmed it. Now you have some decisions:
1. You can try to live with that water and replenish the sequestraunt every so-often as required; that gets old quickly.
2. Exchange a good portion of the pool water for non-iron water, hoping the new water does not also have iron in it
3. Increase your FC level to normal levels based on your current CYA (see the FC/CYA Chart), and when teh color changes, filter continuously with polyfill material in your skimmer to try and catch the iron and reduce some of those metal levels.

Managing a pool with iron is no fun, and keeping the chlorine as low as you are is asking for algae. (if not already present) When you get algae, you need to follow the SLAM Process first before re-addressing the staining.

Don't forget to stop at our ABCs of Pool Water Chemistry page and update your signature with all of your pool and equipment info. Make sure to include which test kit you have on-hand. If it's not a TF-100 (link below) or Taylor K-2006C, that should be priority #1. Pool store testing is almost always flawed and followed by poor advice and over-priced products. let us know if you have any other questions.