Yellow tint on bottom of deep end

[cmcq]

I have a 22k gallon gunite pool with a SWC. Within the last month, a yellow tint has appeared at the bottom of the deep end. It is only in the deep end (8 ft), and only on the bottom of the pool, not the walls. There is a pretty clear line where the tint stops when the bottom of the pool starts to rise to meet the wall. I shocked the pool and it had no effect. I tried the Vitamin C test and it had no effect (earlier in the year we had a metal stain problem and the ascorbic acid worked like a charm). I've tried brushing and that didn't do anything either. Any ideas? I don't have current chlor, ph, etc. since we just shocked yesterday, but the chlorine is typically around 3 and ph is 7.2 to 7.4.

Thanks in advance.

[duraleigh]

What's your CYA level?

[cmcq]

We've just had 2 days of rain so this is the first chance I've had to get the readings:

FC = 1 (it isn't always this low. I had turned down the SWG when I shocked it and forgot to turn back up)
CC = 0
ph = 7.8 (prob higher b/c rain - I'll treat with acid tonight)
Cal = 220
CYA = 29
temp = 72 (down 8 degrees this week thanks to the rain and much, much cooler weather)

Any thoughts are appreciated.

[mbar]

What did you shock for? Did you try to rub a trichlor puck on the stain? You can also put some ph down in a sock and rub it on the stain. If the stain comes off with the ph down, then it is probably metals, if it comes off with chlorine then it is organic. You may not have had enough of the vitamin c to make a difference. Did the stains come before the the shock? You wouldn't get any metal stains from low chlorine and low ph, that is why I would guess that if the stains cam e before the shock, the stains would be organic. Let us know if either the ph down or the chlorine work.

[cmcq]

The stains came before the shock. I shocked thinking it would take care of the stains since the small vitamin C test didn't have any affect. I'll try both the ph down-in-a-sock and trichlor tests, but I have a really dumb question about the puck. I have "stabilized chlorine sticks" (brand and item: Bioguard Stingy Sticks). The active ingredient is trichloro-s-triazinetrione. Is that the same as the trichlor puck you mention?

[cmcq]

It looks like metal stains. I had some ascorbic acid from my metal stain issue earlier this summer, so I put some in a sock and sunk into the deep end. Within a couple of minutes, the area around the sock turned darker brown, and a clean white trail emerged in a line between the sock and the main drain below it. I assume the darker brown was the stains lifting off the bottom. The darker stain did significantly lessen after a few minutes, but I assume that could be the ascorbic acid in the pool. So... do you think I need the full ascorbic acid treatment or should I just try some metal stain remover?

[aylad]

I have "stabilized chlorine sticks" (brand and item: Bioguard Stingy Sticks). The active ingredient is trichloro-s-triazinetrione. Is that the same as the trichlor puck you mention?

Yes, it's the same thing.

Janet