I have a 30 foot round pool. About 4 and a half feet depth with a 6'2 deep end. My pump quit and the valve head on my sand filter is very hard to turn to filter and to backwash. It's about 12 years old. I am looking for replacement and want to know 1. Can I go to a cartridge filter? 2. I am told I need a 1.5 HP pump and 24 inch sand filter if I go back to that. Would anyone recommend just replacing the top valve piece and buy a new pump. 3. I have come across an "off brand" pump and filter...if we are selling our house, would anyone go this route. Lastly, while researching, how come so many people use rigid piping and not flexible hose to connect everything. Please help! Thanks