Not sure about the size of pump or filter, nothing on the outside to tell me but the filter holds 200 lbs of sand so maybe 21" and the pool is a 27ft round. When I cleaned the filter I just used the liquid that you pour into the skimmer and backwash out. If there were any cracks would they be visible on the outside because I didn't see any. Yes, we are using pool sand.
I know this isn't alot of info but thanks for your help!