On Sat, 27 Jul 2013 10:21:51 +0100, Chris Hogg wrote:

... these are due to stress failures in the moulding of the butt with
the tap, around the tap-hole, because the taps are rather stiff and
cause the butt to flex slightly.

Yep, that's what caused failure here though it was the plastic tap
that gave up rather than the butt. That's why I have the ball valve,
very easy to operate so much less force transfered to the butt. Also
better flow.

--
Cheers
Dave.