Hmm. Have you counted the number of recent threads where people are having
problems with pressurised systems?

The problems with the pressurised systems have been nothing to do with being
pressurised, though. They are mainly leaks. The reason you don't see quite
so many issues with non-pressurised systems is that the water just dribbles
away for years (causing timber rot) and gets replenished without anyone
noticing.

Christian.