Reasons for a leaking post

Right, so after fixing the issue with my Q/D - yup, managed to wash out an o-ring out of the top of the screw top of the Q/D and now have a new one - I reconnected the picnic tap perfectly fine this afternoon. Then, when trying again tonight it started leaking from the bottom of the Q/D.

So here are my complete kegging rookie questions. Could the following things have caused beer to foam out the bottom of the Q/D:

1: massively over-carbed beer, because it most certainly is now - oops!
2: overly tight screwed on top part of the Q/D - do I need to bac that screw off a bit?
3: or have I just buggered the seal on the post somehow?

1) No.

2) Possibly, but unlikely

3) How's the post o-ring look? Is it new? Try putting some keg lube on it.

I'd definitely suspect the post o-ring. I had a QD that had some molding flash that would nick the post o-ring every time I plugged it on. Took an exacto knife to it and that fixed it for good...

Cheers!

If it leaks with the QD attached, it's the post oring. If it leaks without the QD attached, it would be either the diptube oring or the poppit.

Cheers for that, turns out it was the post o-ring. Sorted now and beer is back on tap!