Do I have a filter problem?

A little background since I'm new here.

Located just outside Toronto, Ontario, Canada

We just moved into our house 2 weeks ago. The house was vacant since January. Pool was not officially opened prior to house closing. Started to get the pool filled up to proper level so I could run the pump. After 4 hours of running the pump the pool level dropped 3 1/2 inches and stopped pumping. Found wet areas in the interlock near one of the returns. After a $650 quote from a company to repair the leak, I decided to repair it myself. After the less than $20 in materials and about 2 hours of my time, including the drive to Home Depot, the pool was ready to fill again.

So now I am in a situation where there were LAYERS of crap in the bottom of the pool from the previous owners (neighbours have said they never vacuumed it last year). Eventually I put on my scuba mask and fins and got most of the stuff out by hand including the concrete garden edger, concrete cinder block and small cast iron candle holder.

I am doing a lot of backwashing due to the poor condition of the pool. Essentially I am doing a pool opening in July. Every time I vacuum, I do it to waste. What I am noticing is a lot of sand depositing on the bottom near the shallow end return. Should I be concerned at this point. Is it just the high activity of the filtering and backwashing? Could sand have gotten into the line from the crack in the return line? Or am I looking at a repair of my sand filter?

Does anyone have and suggestions?

Sorry for the long expanation.
:confused:

I would first confirm it's coming out of the return by covering the return with a nylon or something to catch the sand.

If it's from the return, My best guess is you've got a filter problem. The most likely issue seems to be broken laterals which are easy to replace but the sand has to be removed....pretty much of a PITA.