Dark Greyish stain removal?

bosco

Bronze Supporter
Aug 7, 2019
17
arizona
Hi - this house was purchased about 2.5 yrs ago, and since then I have had two types of stains found on the pool - one green/yellow and likely from organic algae growth. I removed most of it by directly putting vitamin c on areas. The other are dark grey "stripes" which sometimes have some yelowish areas too.

The pool has been slammed a couple times with no reduction in dark gray stripes. pool water was tested and both iron and copper were found low. I dont use a copper-based algecide, but previous owner may have. I have not fully drained pool since purchase, but partially (1/2) drained it previously to reduce CYA.

Dark stripes are not black algae, not slimy or round, but do feel a bit rough. I tested with vitamin c by filling sock attached to heavy filled tupperware on a grey area - the stain turned slightly reddish in attached picture the center of the stain had vit c applied

I am currently testing another stain spot with dry acid in a different sock/tupperware.

? Why in straight lines could this be rebar related?
Q:
1) how to treat the remaining yellow stains which are on vertical walls w vit c?

2) Thoughts on dark line stains?fullsizeoutput_9e0.jpeg
 

bosco

Bronze Supporter
Aug 7, 2019
17
arizona
Oh, by the way, these stains were not on the pool when purchased. some months after purchase (6?) one started to appear, and others continued to slowly appear and grow over 2 years.
 

bosco

Bronze Supporter
Aug 7, 2019
17
arizona
Ok, now its strange.. a few hours after the stain turned more reddish, it faded to about 10% of what it was... So maybe it is iron??
 
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