Draining and refilling an unvented system

I have searched and trawled this site and the net, but can't seem to find anything whihc explains how to do this.

I have an unvented system, and am gutting my bathroom at present.

I am now at the stage where I need to start changing tap/shower pipe locations, and plan to stick isolation valves just where the hot and cold pipes come into the bathroom so I can put the water back on and take my time to sort out the bathroom while using the water in the rest of the house as normal.

How do I safely drain and refill the hot water system to do this?

I can find the mains stopcock, and also a valve which if opened would rain into the pressure/expansion relief discharge pipe.

Presumably though, I need to "vent" the system to clear the vacuum to allow it to drain though(?)

wouldnt open the pressure relief valve if i was you,most of the time the will not re seat properly.

Shut off mains, open hot taps. That will drain most of the pipework, if you need to drain cylinder connect hose to drain-off valve at the base where the cold feed connects.

Thanks. Preumably when I refill I won't have any pressurisation problems?

you wont be emptying the central heating system just the water in the pipework for your taps/shpwer etc-no need to refil-just turn mains water back on and open taps.

cjb1971 said:

you wont be emptying the central heating system just the water in the pipework for your taps/shpwer etc-no need to refil-just turn mains water back on and open taps.

Click to expand...

Even with an unvented system?