On Thu, 04 Dec 2008 09:55:49 +0000, John Rumm wrote:

I remebber a couple of recent fatal incidents with vented cylinders...

IIRC not caused by failure of the cylinder but by bad installations
allowing hot water to circulate via the plastic header tank leading to its
failure.

never heard of any with unvented in this country yet.

Maybe the guidelines regarding installation and/or inspection mean that
bad installations are very rare. ducks

--
Cheers
Dave.