Loss of pressure range tribune HE

[Edwards19]

morning,
I fired up my central heating on Sunday and bled 2 radiators ( they both hissed but no water came out) all the others were roasting hot and now I have no hot water. I can see the pressure has dropped on the expansion (?) tank to zero but I don't know how to get it back up and even if this is the right thing to do......
Thanks in advance

 

[muggles]

It sounds like you've depressurised your heating system. Post a photo of the red expansion vessel and the pipework around it

 

[Edwards19]

 

[muggles]

OK, silver hose with a valve at either end - open both valves until the black needle on the pressure gauge goes into the green zone, then close them again. You might need to bleed some air out and repeat this

 

[Edwards19]

So sorry for the next question - should I keep turn everything off before doing this? I turned my boiler off at the mains when I realised I had a problem
Thanks

 

[Edwards19]

I've braved it, all sorted out..... thank you for your help muggles