Suddenly my downstairs toilet stopped filling this week, I suspected a blockage in the filter or cistern itself, however after removal of everything it appears that there is no water coming in, its mains fed and no sign of leak anywhere , we have checked the isolation valve and its not faulty, the pipe below has this connector on it? can anyone advise, there also seems to be a similar fitting on the pipe as it disappears into the wall. Both me and my plumber are flummoxed! Could it be blocked? have used a vaccum on it .. any ideas very welcome, all other taps etc in the house are fine, which is why it seems very odd.