Issue with Sand?

Pool went unused for 2 years. Full of leaves, algae, frogs, etc. I have managed to clean all that out. My chlorine, calcium, ph ,etc. are all near normal range. The problem is the pool, after running the filter for over 72 hours straight is still cloudy blue. When I put the vac pole in I can see about 2 feet down and that is it. When vacuuming on the filter setting dirty water was coming back in via the jets right away so I switched to backwashing to waste. When I do backwash, the sight glass never changes color. Doesn't ever seem particularly dirty. When I open the tank drain it smells real strong of algae, dirty water. (I assume this is normal) Filter pressure gauge needs replacing so can't say if that has changed any. The pool was either not cared for at all or very little for the past 5 years. I was planning to test by putting D.E. into skimmer but that is $20 for 25 lbs. so why not change sand at a cost of about $36? I know the thinking is sand rarely needs changing, and dirty sand works better but I also saw on here were it was suggested if pool is still cloudy blue/grey then it could be sand. If not sand, then is there a clarifier you would recommend? First time pool owner so very new to all the chemistry, etc... Thanks

Have you been able to inspect the sand? Is it at the right level?

I don't understand, you were vacuuming with the filter set to backwash? Wouldn't that make the clean side of the sand dirty?

You should be able to find a 10lb bag of DE.

Adding DE to a sand filter is sometimes suggested as a means of determining if your filter is working properly. If it isn't, then changing the sand isn't going to do anything for you.

Turns out the pipe inside the sand filter is broken in multiple places. The cpvc it is made of is not readily available in that size and the whole unit w/laterals is $75.00. Anybody know if I can 1 1/2" sched. 40 instead?