Black ‘smudges’ in new pool

mxfan

LifeTime Supporter
Jul 24, 2008
68
Shingle Springs, CA
Hi all,
We had a pool built last Winter and about half way through our swim season I noticed a few small black spots in the bottom of our pool and one up near the tile near the water line.
There are 3-4 spots and in Summer I could scrub them with a brass brush and get about half of the black to go away, but not the entire stain.
We use a swg and fc levels have never fallen below 4-5 ppm so I can’t see how it would be black algae.
Current test results:
FC 5.5
PH 7.5
CH 350
TA 80
Water temp 55

Any ideas?
 

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YippeeSkippy

Mod Squad
LifeTime Supporter
Jan 17, 2012
13,312
Evans, Georgia
Ok, lets try a couple of things. Grab some Vitamin C cheap chewable tablets and stuff some in a thin sock or nylon stocking leg and smash em up a bit. Hold that up to the stain near the tile for a couple of minutes and see if that changes anything.

If it didn't, go buy a single chlorine puck (or grab one from a neighbor who hasn't discovered the problems with puck use yet, lol) and rub that on a for a few minutes to a different stain.

My worst fear is that its a smidgeon of rebar showing thru and you'll need to have your pool builder assess that.

Maddie :flower:
 

mxfan

LifeTime Supporter
Jul 24, 2008
68
Shingle Springs, CA
Ok, lets try a couple of things. Grab some Vitamin C cheap chewable tablets and stuff some in a thin sock or nylon stocking leg and smash em up a bit. Hold that up to the stain near the tile for a couple of minutes and see if that changes anything.

If it didn't, go buy a single chlorine puck (or grab one from a neighbor who hasn't discovered the problems with puck use yet, lol) and rub that on a for a few minutes to a different stain.

My worst fear is that its a smidgeon of rebar showing thru and you'll need to have your pool builder assess that.

Maddie :flower:
Thank you for the reply! I was wondering if that was a possibility even though pre-gunite they spent a few hours looking for rebar and metal wire and I even looked around some as well.
I will get a chlorine puck and see what that does for it.
Thanks again!