I didn't want to hijack 65corvette's post, but I've had the same problem ever since I put the pool 4 years ago. Each year, I get the water balanced and things look great until end of July /early Aug, then my pool turns green, and I fight it for a month and a half with shock, but it never really clears so give up and close it for the winter.
I've never had any indication of Cl drop overnight and my water is actually reasonably clear until I brush the green/yellow deposits on the bottom. This year I thought that maybe it could be pollen (as shown in photos of other posts) as the deposits are on the bottom and sloped walls.
This year I kept and monitored my Cl to between 5 and 10 (SWG recommendation is 1-3) for the entire season just to make sure but I have the same issue.
My numbers are as measured on my Taylor K2005 test kit
Salt =2800 (SWG)
I have noticed that the deposits form within an hour of the pump/filter being turned on.
I vacuum them up and then backwash. But they do not seem to form when the pump is off.
Thinking the deposits could be algae in my filter I poured shock amount bleach direcly into the filter and let it sit for a day, but no change.
I plan on doing the following experiment.
Run pump and filter
Run pump in re-circulate position
Do not run pump.
Repeat above with the solar cover on to see if there is any difference in the 6 scenarios
This is complicated by the fact that my vacuum cleaner always gets hung up as the liner floats about 1/2" from the wall in one area of the deep end, so auto vacuuming is difficult. I have checked with the city and the water table in our location is far below pool depth. During the pool build in April/04, there was no evidence of any water source/spring. I have done the 'pail' test and found no evidence of a leak. So the source of the water is a mystery
I do have a couple questions.
1) I notice that the shock level for Mustard Algae is 34ppm. Wouldn't this damage the liner?
2)The water behind the liner has always concerned me, could it be a complicating factor?
There is a pool store that recommended some sort of electronic leak test for $150,
Would you recommend this?
I'm getting frustrated and to top it off, I don't think it is my methods as I maintained a neighbours 30 yr old vinyl pool that is in need of major upgrade, and thanks to what I've learned in this forum, it was very easy.
Any help you can provide would be great.