I changed the 4 cartridge filters out yesterday on my Hayward Swimclear C5530 Filter getting ready for the Fall and Winter. Now, the pump won't stay primed once I turn the filter off. There is no leakage at the seal where the filter comes together. It has been difficult to turn off the manual relief valve at the top of he filter which will release some water and air for a few minutes but will finally stop. Do you suppose there is a small amt of air that continues to release until the pump and filter lose prime? Do you have to replace the entire pressure gauge on top to replace the valve or can you replace the valve by itself. Thanks in advance for all your help.............