Today I was prepping pool so we can go on a vaca. Of course, things took longer than expected especially when I came across the following situation with my Hayward cartridge filter 450 (I am using Filbur FC-1275 cartridges). I had just finished emptying/cleaning the strainer basket that is in my pump, and then poured water into my pump in the strainer basket. Turned it on, had the pressure relief valve at the top of the cartridge filter open to let out the air, and turned on my pump. It was priming at 3000 RPM and things initially were going okay. After a little while, all the air was released and water started shooting out as it usually does at 3000 RPM. But then, the amount of water that was shooting out started to become incrementally less and less, to the point that even at 300O RPM it was just squirting a little out (not projecting out like it normally does).
I turned off the pump, opened the pressure relief valve, took off the drain plug for the cartridge, and took off the top. Looking inside the top cover, I didn't notice anything jammed or caught in the inside of the valve. Nor did I notice anything out of the ordinary in the inside of the cartridge housing. So, I put the top cover back on, secured the clamp, put in the drain plug, and made sure the pressure relief valve was open, then started it back up again. Same thing, water was just very gently squirting out the pressure relief valve at 3000 RPM. During this time, I checked the pool jets/returns and they all had the normal pressure they should. I also have a FlowVis, and it was looking normal was the amount of flow it showed I had. I checked the pressure gauge on the top of the cartridge, and it showed I had a little less pressure than normal. I think I may have broke it or something b/c before I took off the top of the cartridge, I was trying to loose that entire pressure relief valve/gauge assembly. I turned it counter clockwise but then turned it back, but I heard it crack or something when I tightened it.
I am basically curious what is going on. If it is related, one thing is that lately, perhaps one time per week, I notice my cartridge loses its prime and I hear the water bubbling inside it. So, I would turn up the RPM and purge the air.
In advance, thanks for any help. When I get a a chance I'll try take/post some pics of the pressure relief valve/area.