The pool is 18' X 54" deep with a Hayward power flo lx 1.5hp with a hayward cartridge sw110mpaks filter. I need a new pump and I'm thinking I do not need 1.5hp, but don't know for sure. Also I can buy a Hayward 18" sand filter really cheap from a friend, model S180T. I'm thinking a 1hp hayward Matrix pump or a dynamo. Would I be O.K. with a 1hp pump? Would it be an upgrade buying the sand filter? I also have a 8gal liquidator on the system? Any help and recommendations are much appreciated!!!