Interesting. I discussed this with a guy on Whiteblaze. We have both had the problem where the red check valve "puckers up" during the back flush not allowing anything through it. The only way to resolve the issue is to take the filter back apart, pull the valve off, start over and hope it works. Is this the airlock problem being referred to in the BPL thread? Is my filter now "broken" and in need of being replaced?

I'll be interested to hear input from others and Jason on this.