Hello my name is Carlee, and I am new to this site and somewhat new to having a pool. Recently moved in with my mom and step dad who have a huge 40k gallon inground pool in their yard and for 20+ years never even bothered to learn any maintenance on it at all. I have learned how to balance the chemicals in the water perfectly and basic maintenance of keeping it clean. However, I have noticed a drop in the return line water pressure and am sure that I need to replace the sand in my filter because it has been years since this has been done. I have a filter that has been discontinued and the parts I need to be able to put it back together after replacing the sand are no longer available anywhere online. I need to get another filter to replace the one that is now obscelete and don't know what to replace it with. It's a PacFab SuperFlow PF50 sand filter that is 22" and the clamp screws are rusted and if I undo them I will not be able to put it back together and have it be able to be air tight. Any advice you have or you can recommend what my next step should be would be very appreciated. Thank you so much