Why the crazy iron staining after SLAM?

[Jellwood]

Greetings:

Letting FC levels drift down after a successful 7 day SLAM. We have been battling iron staining from our town fill water (have to top off daily) all season. It’s definitely iron. Have temporarily cleared stains different times with AA treatment and Metal Magic and polyfil in skimmers.

It was faint but present during the SLAM. This time stains are noticeably worse daily as I’m letting FC levels drift down. I’m also using a floater and pucks because I can’t hold CYA...

Question: is there a reason why the stains get worse as the FC goes down?

we’re doing a liner replacement this fall. I’ll probably do another MM treatment just because it looks pretty bad even though I know it’s temporary. But I’m curious why it’s worsening now.
This morning:
FC 9
CC 0
Ph didn’t do because it’s still high FC from slam.
TA 70
CH 120
Thanks all!

 

[Texas Splash]

Question: is there a reason why the stains get worse as the FC goes down?

We can assume your pH is elevated which is probably the culprit. We know the iron was aggravated during the SLAM, but I would verify that pH and lower it right away to something like 7.4. That may help quite a bit.

 

[Jellwood]

We can assume your pH is elevated which is probably the culprit. We know the iron was aggravated during the SLAM, but I would verify that pH and lower it right away to something like 7.4. That may help quite a bit.

Hi, Texas Splash!! Thanks for the reply. I Checked the PH last night and it was 7.4. Dumped a bottle of MM in the shallow end where staining is worst and filled the skimmers with polyfil (enjoyed seeing the confusion on the face of the pool guy giving us a Reno estimate when we saw the polyfill in the skimmers. “What is this white stuff in here?” He asked skeptically. I explained about our iron in
and how it helps, and he just shook his head, chuckling to himself. “Never heard of that one before. WHO told you to do that?”

Will keep letting FC drift down today and see what happens.

question: why does the MM work best at a high PH & super low chlorine?

FC 9
CC 0
Ph 7.4
CYA 30

 

[Texas Splash]

why does the MM work best at a high PH & super low chlorine?

I'm not sure if it's really working better, or just that at a higher pH the stains tend to show more, so it appears to be working better. You can see from the Magic Jack's instructions HERE that the pH needs to be quite low when treating. Your FC is a bit high as well which probably is aggravating the iron. That should fall soon though I would think.

 

[Jellwood]

I'm not sure if it's really working better, or just that at a higher pH the stains tend to show more, so it appears to be working better. You can see from the Magic Jack's instructions HERE that the pH needs to be quite low when treating. Your FC is a bit high as well which probably is aggravating the iron. That should fall soon though I would think.

Gotcha. Looking better already today!