Good afternoon...I have a Sta-Rite System 2 Filtration System (Model # PLM100) for my pool. I was told by our installers that my cartridge should last me around 5 or so years. I am on year 3 of my pool and I am on my 3rd filter. I have to clean it on a weekly basis as well as soak it on a monthly basis. In order for the flow to be right I have to at least keep the pump running on 3 out of 4. Any help or advise on what might be causing this would be great.