I am now in a  house with  an unvented water heater & boiler, and have never come across these sytems before, so have no idea how it is plumbed in, or more importantly, what to do to turn off the water to change a washer in the bathroom on the first floor! (actually I'll go round and change them all while I'm at it). There only appears to be only one valve in the airing cupdoard on the second floor? Does anyone have a link to a good diagram of how this set-up works?
None of the sinks, baths, showers etc. appear to have isolating valves on them! I suspect this could turn into a right bundle of fun.
Oh dear.....

It's a Glow worm Ultimate 100FF on the ground floor, A/S OSO 250l unvented water heater on the second floor. I was looking for a sort of 'generic' diagram of how it is piped, is that not possible?

Many thanks, I turned off the mains & the cock in the airing cupboard & changed a shedload of tap washers in various stages of wear & disintegration. I didn't even think about this with an unvented system, it's easy isn't it
I don't think this was a DIY job, the previous owner definitely wouldn't have been capable. So how many / where should there be cocks? The one there is extremely stiff so if I have to drain it all down to add some I'll replace that as well (with 22mm ball / lever type).
Cheers.....

thescruff wrote on Jun 6^th, 2011, 10:26pm:



Are you sure it's an unvented cylinder.

The reason it say don't drain maybe because of the inhibitor, or the type of cylinder.