Algae but no FC loss on OCLT

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peanutsofdoom

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Dec 26, 2015
24
Moraga, CA
Hi,
Started following the TFP method about a month ago and things have been going pretty well. Discovered my CYA is 50 and I've been using the calculator to add the appropriate amount of bleach and keep the FC within recommended levels.

My pool water is clear, but I get some greenish/brownish dust that's been gathering. I vacuum it up and it comes back. I raised to shock levels and vacuumed but it came back. Seemed like maybe Algae but here's the kicker:

OCLT shows no loss! Tested FC at 6 and then was still at 6 the next morning.

Maybe I don't actually have algea?

My pool gets a lot of debris (pine needles, insects, etc). I run the pump 24/7 at around 25gpm based on an intelliflo calculator (boosted up to 35 gpm for 4 hours a day just for fun and to run the sweep)

Any ideas?
 
Those numbers look pretty good. Is there any chance we could assume your FC dropped below the minimum of 5 based on your new CYA of 60? Maybe enough in this summer heat/sun to allow algae to kick-in? But it is odd that are passing OCLTs. Does that green brush-off easily? Can you grab or scratch any of it and smear it on some white paper to see if it's green? That stuff seems to be going up the side walls a bit in that photo right?

Also, where does your water come from (well, city)?
 
Texas Splash said:
Those numbers look pretty good. Is there any chance we could assume your FC dropped below the minimum of 5 based on your new CYA of 60? Maybe enough in this summer heat/sun to allow algae to kick-in? But it is odd that are passing OCLTs. Does that green brush-off easily? Can you grab or scratch any of it and smear it on some white paper to see if it's green? That stuff seems to be going up the side walls a bit in that photo right?

Also, where does your water come from (well, city)?
Click to expand...

Water comes from the city (EBMUD)

The green brushes off very easily. If I touch it, it basically just disperses into dust. My pool sweep will kick it up from the bottom and leave a clean line in its wake. I will try the paper test later to see if it's green.

It could be that I miffed the CYA test too and that my CYA is closer to 50 (the reagent was slightly above the label when I filled the CYA bottle in the TF-100)

I went on vacation for 9 days and shocked right before I left and put 4 tabs in a floater as well (that would account for some change in CYA, but 10 ppm seems like a lot for 4 tabs, no?). I discovered today that while I was away the sweep was only getting to 1/4 of the pool.

Another odd thing about my setup is my skimmer. The suction can be horrible sometimes and it looks like it wasn't sucking well while I was away. My skimmer has a float valve assembly which must have prevented the suction from working. Seems like an annoying feature. That would account for why the top of my pool had debris, but wouldn't really explain the algae, since the main drain should have been passing the water to the filter still, right?
 
The look of it and description of how it disperses definitely sounds like algae. Poor circulation could definitely contribute. Each tab could add anywhere from 6-9 ppm of CYA, so it's possible your CYA is higher than you thought, thus it would have required a higher FC while you were gone. We'll see if you come back with any more info.
 

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