David Hansen wrote:
On Thu, 4 Dec 2008 15:09:31 -0000 someone who may be "Tim Downie"
wrote this:-

IIRC it was a vented cylinder that just boiled over through the
expansion/vent pipe into the loft tank. Don't think there was any
"safety relief valve" other than the open pipe. In fact, I think
any sort of valve on an open vented system is illegal.

Any sort of valve?

Can't an open vented system have a valve on the feed and expansion
pipe? Can't have valves (presumably including taps) on the domestic
hot water pipes? Can't have a pressure relief valve fitted in case
some vulnerable pipework ices up? Every open vented system I have
seen must be illegal.

Bl**dy pedant. You know what I meant. Valve on the expansion/overflow.

Tim