I have a Sta-Rite modular Media Filter. At start up, you are supposed to open the air release valve until a steady stream of water comes out. Although the air stops coming out, I cannot get a stead flow of water. In addition, the gauge reads 0 pressure. I have replaced the entire air release valve assembly and have double checked the installation of the filters and position of the bleed tube and filter, but the results are the same. Any suggestions?