Brown-ish Spots keep coming back

[atxjmy512]

New pool owner battling brownish spots on one of my benches. They just started showing up over the weekend when I accidentally ran the pool down to 0.15 ppm FC with water temps around 85 - 87. Water looked slightly cloudy and a little green. I shocked the pool that night, and everything from a water chemistry stand point is back to normal. The spots disappeared when I rubbed a chlorine tablet on them, so whatever it is its organic. But these spots keep popping back up almost daily on that bench (though not in the exact same spot) despite the shock. I continue to rub a tablet on them, and they disappear for 12 or so hours and start coming back. It lightens somewhat with aggressive scrubbing, but doesn't completely disappear.

I'm just not sure what it is I'm battling. Given the level of chlorine I added (2 gallons of liquid shock to take it to 20 ppm) I'm surprised anything organic is living. I don't have any metal in the water either, and in any case chlorine makes whatever it is disappear. For what it's worth - I'm in Central Texas and we're dealing with the mother of all pollen seasons, its dumping yellow pollen and dead live oak "flowers" all over the place.

I didn't think to take any pictures, but imagine dime to quarter size yellowish brown spots on the deep end bench (and only the deep end bench) that disappear when chlorine is directly applied.

Thoughts?

 

[Texas Splash]

I'm just not sure what it is I'm battling.

Algae. These "shocks" you refer to are not going to work. That's' pool store methodology. You need to follow the SLAM Process and be sure to maintain the proper elevated SLAM FC level "continuously" as noted on the FC/CYA Levels until you pass all 3 SLAM criteria. Of course you must have a TF-100 or Taylor K-2006C test kit to do this, so hopefully you have one already.

 

[atxjmy512]

Algae. These "shocks" you refer to are not going to work. That's' pool store methodology. You need to follow the SLAM Process and be sure to maintain the proper elevated SLAM FC level "continuously" as noted on the FC/CYA Levels until you pass all 3 SLAM criteria. Of course you must have a TF-100 or Taylor K-2006C test kit to do this, so hopefully you have one already.

I figured this was the case, was just hoping it wasn't. My K2006C is on order, it should be here Thursday or Friday.

 

[atxjmy512]

I've never slammed before... I think I understand the process and criteria - but I need to keep the FC at the Slam level for my CYA correct? At least until the 3 criteria are met?

 

[Texas Splash]

but I need to keep the FC at the Slam level for my CYA correct? At least until the 3 criteria are met?

Correct. So once you get the test kit, get an accurate CYA test result first, then go to the FC/CYA Levels to find what your SLAM FC level should be. Before increasing the FC to SLAM level, be sure to lower the pH to about 7.2. But if you follow the SLAM Process you should be in good shape.

 

[atxjmy512]

So... interesting wrinkle... I'm currently passing SLAM criteria ( I have 0.5 or less CC, I passed a OCLT, and my water is clear) even though I have not yet started a SLAM. I'm no expert, but from what I've read about SLAM I think that means there's nothing organic in the water consuming chlorine, correct? And if that's the case - could this actually be algae or might it be tannin staining from debris landing on and sitting on the bench too long (I've been fishing out small sticks / branches all week due to high winds)?

 

[Texas Splash]

from what I've read about SLAM I think that means there's nothing organic in the water consuming chlorine, correct?

That is correct. So you might have some organic staining which you can test by rubbing a chlorine tablet on the area. Don't let it sit though. Move it around to see if it lightens the stain. If so, you may need to keep the FC elevated for a while with consistent brushing to help lift the stain.

 

[atxjmy512]

That is correct. So you might have some organic staining which you can test by rubbing a chlorine tablet on the area. Don't let it sit though. Move it around to see if it lightens the stain. If so, you may need to keep the FC elevated for a while with consistent brushing to help lift the stain.

I haven't. Ive been checking that area a couple of times a day and rubbing a tablet on it - and it almost immediately disappears. My FC has been holding at around 10.5ppm since I shocked it last weekend (its been cloudy here in Austin, so no real direct sunlight boiling the FC off).

I have notice some bird droppings on my coping in the immediate area, and fished some off of this bench yesterday. I'm almost positive a spot later formed in that exact location. Could this be my culprit? While the spots are in the same general area, they are almost always in a different location every time one shows up and i have trees limbs directly overhanging this section of my pool (I will cut them away when I can safely avoid oak wilt in June).

 

[Texas Splash]

Tannin staining from the oaks is certainly a possibility.

 

[atxjmy512]

Tannin staining from the oaks is certainly a possibility.

Confirmed. The lawn guy had just finished, and I was skimming debris out of the pool, and noticed a spot forming. I put on a pair of goggles and happened to catch two pieces of dark debris sitting on a new spot. They floated up when I disturbed the water. At least I know what's happening now. Cannot wait to trim these trees.

 

[Texas Splash]