I've browsed all the other algae posts, but couldn't resist asking my own personal questions.
I have a 24', 52", above ground pool with vinyl liner. Hayward dream line filter with 1.5 hp power flo pump. We live in Missouri, and the pool receives sunlight all day (no shade at all).
When we opened our pool this spring, algae bloomed viciously as we replaced parts on our Hayward sand filter. Every time we thought we had it, a leak would spring elsewhere. The equipment is only seven years old - we have replaced all of the easy to reach gaskets, hoses, the control valve, the pressure gauge, the sand and the laterals within the past year. Things seem to be running smoothly now, though I fear there is something broken inside the pressure gauge area, as it seems to always be at 10 when running, even when there is a noticeable difference in return flow. When we replaced the control valve, we only replaced the actual valve (with the handle), so I guess the next step is to replace the other part of the valve assembly.
Except...the algae won't go away. I kept shocking and shocking, then realized the shock had stabilizer in it (sodium dichloro something or other), as well as the pucks I was using. So, after stumbling on this site several times, I stopped using those and began using calcium hypochlorite shock. All I had was a Walmart 6 way test kit and test strips, but from what I can gather the CFY was up to 120 - not too bad - and for the past 36 hours I have kept the FC level at or above 25 (using the test kit drops with dilution as described elsewhere on this site). Which is not quite shock level for the CFY level, according to the chart, but should be adequate to make a difference, I would have thought. With the vinyl liner I was afraid to go much higher than that.
The filter has been running 24/7 for about 10 days, except for a couple of overnight halts to see if anything would settle. I last added algaecide 4 days ago, ran for several hours, let it stand over night, clarifyer 2 days ago.
There is no noticeable gunk on the bottom to vaccuum for about 4 days. I've vaccummed once a day for four days, we last went swimming four days ago and made sure to rub the walls and floor (which wasn't slimy at all). The water is still green and murky - visibility about 12 inches - no visible change. I feel like I'm missing something. There is slight algae growth on the ladder - other than that it is just the green, cloudy water.
I have drained the water to the skimmer level (about 4 inches), hoping to bring the CFY to more like 100, and plan on shocking again this morning once I've refilled the water.
Even if the filter is not filtering well, it is creating good flow (I would think, judging from the power of the return and the rotation of the water in the pool), the FC is adequate, and I am stirring things around several times a day trying to brush the bottom.
Sorry for the long rambling post - there's been a lot of circumstances I wanted to relay. I'm tired of spending time and money on a pool that no one wants to swim in, that I'm not sure is safe to swim in. I am ordering a Taylor test kit, but that won't help me now. Is there anything I'm missing here?