Cannot get my cloudy pool to clear up after killing algae

[Ranscon]

I have an above ground pool.
Vinyl Liner
13,500 gallons
FC 5PPM
ALKALINITY 90
PH 7.5
24 inch sand filter 1 hp pump motor.
I use stabilized 3" tabs for chlorine
DON'T HAVE A TEST KIT FOR CALCIUM OR STABILIZER
After the winter it was very dark green. I have shocked and shocked, bleached and bleached, used two full quarts of algaecide 50, used a whole quart of floc in 2 or 3 different doses. vaccuumed, shocked some more. The algae seems to be dead. The water is now a light grayish blue color but will not get clear. I have just replaced the 300 pounds of sand in my filter with new pool filter sand. I've had enough. Today I put in clarifier 1 oz per 5000 gallons. I have added about 14 to 16 ounces. Should I leave the filter running 24 hours a day till it clears? or should I turn it off and let it settle so I can vac it out? I've been working on this for 5 weeks now and I've tried both methods. NOTHING WORKS. PLEASE HELP. Thanks, Jeff

[chem geek]

Since this is an above ground pool with a vinyl liner, it is likely that it does not have a floor drain. That makes circulation from the bottom of the pool poor. Also, a sand filter doesn't filter as well as DE or cartridge. However, you should really get either the Taylor K-2006 test kit at a good online price here or the TF100 test kit from tftestkits.net here with the latter kit having 36% more volume of reagents so is less expensive "per test".

There are two things you can do to clear the pool more quickly. One is to add a small amount (about a cup; maybe less if your filter is smaller) of DE to the sand filter via the skimmer (see here). This will remove finer particles, but note that the procedure has to be repeated after you backwash. This is generally something to do when you don't have to clear up algae -- it's better to keep the pool clear rather than to clear it.

The other thing you can do is to use a powerful flocculant. You can use OMNI Liquid Floc Plus (from here, for example) or Alum from Leslie's here. You turn off the pump soon after adding the product, then vacuum to waste after things have settled to the bottom.

Richard