This is my first post as I am new to this site. I have a 24' above ground pool with a sand filter, and 1 hp pump motor. I just replaced the sand in my filter and it seemed to do fine for the first week as I was trying to clean and filter the water. For no apparent reason the water seems to not be going thru the sand in the filter but seems to be going directly into the skimmer and out of the return. Also when I turn off the pump the water gushes out of the top of the skimmer at least 4 to 6 inches. When I try to backwash, the waste water takes about 20 to 30 seconds to begin flowing. The pool water also is not clearing after putting the chemicals in that I usually open the pool with. I had the water tested and put in the recommended amount. At any rate there is either something wrong with the filter itself, the multiport valve, or there is air somewhere in the system. This is an old Jacuzzi filter (13 years old) and I don't see any bleed valve anywhere to bleed off excess air. Does anyone have any ideas. This is a first for me as this has never happened since I have owned the pool. I bought it new 13 years ago. The multiport valve is a 7 port valve which includes Filter, Drain, Test, Backwash, Whirlpool, Winterize and Rinse. I am at a loss as to what to do next. Thank You!