When you have screwed the fillter out, at the back of where the fillter fits there should be two out let pipes.
When the same fault happend to mine there was a button stuck in (you could not see it) one of these pipes.
It was just lucky that there was some thread still hanging from the button and i was able to pull the button out by the thread with a pointy nosed pliers.
Saved £30 call out fee and it has worked ok since
Robert, July 2010
