I'm a first time pool owner, and I need lots of help. I know literally nothing about any of this, but I'm learning. I have an above ground pool with in ground plumbing. My filter is a Sta Rite Posi Clear cartridge filter. I hired someone to open my pool two weeks ago and after one week of running they recommended I clean the filter out. I turned off the pump and tried to drain the water in the filter but water just kept on coming out of it. I was told to close the pipe by the pump and on the return, which I did, but water just kept on coming out. I wound up unscrewing the top and removing the filter, then I screwed the top back on to keep the water from overflowing. I hosed off the filter, opened the top back up, put the filter back in, and closed the top. I feel like the water shouldn't have been continuously flowing in when I opened the filter. What am I doing wrong? Any help is greatly appreciated. Please speak in layman's terms as I am a novice at this whole pool thing.