Sorry for the length of this....
For a couple of weeks, I've been fighting a tendency for my pool water to go ever so slightly cloudy and green-ish. FC levels and PhD were always kept quite good (FC between 7-10 and Ph 7.4-7.8), with almost never any evidence of CC. CYA os good too, somewhere between 40 and 50. (Water temp. high however, at 85 degrees.)
Still I am being plagued with considerable amounts of what I *think* is fine and loose dead algae drifting on the pool bottom (there may well be pollen there too), and while it does come up with a vaccuum, the next morning it will be there again. Moreover, whenever I start the pump up after vacuuming, I get a pretty substantial stream of cloudy water coming out of the return jet--it lasts for about 7-8 seconds.
This morning I pulled the valve assembly off the top of my sand filter, and discovered quite a bit of green algae growing on the inner walls of the filter. As well, a layer of algae had spread across the top of the sand, extending about two inches from the wall. This algae seemed pretty healthy, so to speak. After excavating the algae--or miost of it--I poured a good bit of straight bleach around the top of the sand and on the inner sides of the pump.
I've since dug out the algae by hand, and am going to pick up a bit of filter sand later this morning. I plan to remove much of the sand from the filter, have a look at the bottom of the filter assembly to see if anything's amiss, and then fill with new sand.
I just want to ask the board if there's anything else I should be looking for, and perhaps also what might have brought on the algae growth in the filter. We did have a very mild winter, and although I drained the pool and filter, I'm sure the inside of the filter remained damp over the winter. My pump tends to run at about 10psi.
best and thanks to all,