please help ASAP!! I can't seem to get to the inside of my filter to even see if there is sand...I have the inlet and outlet pipes disconnected as well as the backwash pipe disconnected. I cannot for the life of me get off the top of the filter --- do I just keep twisting? It wont' even budge ---- I have opened the air and water tubes -- even took off the screws that hold the switcher on -- please help me!!