I'm having a problem with what I think is water pressure in my return lines. I believe it to be a pressure problem because I have three returns, one in the deep end, one in the shallow end and one for a slide. The water has stopped flowing out of the slide. The water pressure in the deep and shallow end returns seems to be ok. Also, the pressure gauge on my cartridge filter housing is around 27 psi when it usually runs around 20. My pool is 6 years old , it is a 16x32 vinyl inground pool with a Sta-Rite Cartridge Filter and a Sta-Rite pump. I've had the pool open since early May with no issues until today when I noticed that water wasn't running down the slide. I cleaned the filter cartridge, the pump basket and the skimmer basket and restarted the pump, the intake valve to the pump was between drain and skimmer(half way) - water began to flow out of the slide but it wasn't flowing as vigorously as it usually does and it eventually stopped(I didn't notice how long because I didn't return for a couple of hours at which point I realized it wasn't running down the slide). After I noticed that the water had stopped flowing down the slide, I stopped the pump, opened the valve on the top of the cartridge housing and took the lid off of the pump to reintroduce some air into the system, then I closed everything up and restarted the pump - once it primed and all of the air was forced out of the system, a very small amount of water began to flow from the slide but stopped after a minute or two. I'm stumped. Thanks in advance for any suggestions/advice.