In article ,
Tony Bryer wrote:
I thought that one of the features of sealed systems was that - in
the event of a leak - they should only spill a couple of litres of
water before running out of pressure. Is this not so?

A finite amount of water: initially the volume which the expansion
vessel has taken up when pressurising the system and then the rest of
the water in the system above the hole - either a steady drip, or at a
greater rate if an AAV in the boiler or elsewhere is letting air in.
But at some point it will stop whilst with a gravity system and header
tank supply not turned off the water will flow indefinitely.

True it will, but a well designed 'open' system will in fact 'consume'
very very little water, so doesn't need a full flow feed. If you really
are worried about the possibility of a flood, fit a flow restrictor. You
could probably set this at something like a maximum of a litre a month, or
even less. The standard header tank for an open system will last probably
about two years before running out on a well designed system.
Basically, pressurised systems are a con for most houses. Fine if space is
at a premium, or in a flat, etc.

--
*If God dropped acid, would he see people?

Dave Plowman London SW
To e-mail, change noise into sound.