Stuck valves

[Brigadier]

Hello

I need to replace a broken monoblock mixer kitchen tap. The only working isolation is on the rising main.
The hot water valve under the combi is solidly open.

If I shut off the rising main, switch off the boiler, then open all of the taps to release any residual water, will that be ok for me to then change the kitchen mixer?

By not being able to shut off the hot at the boiler, would I risk an airlock when I open the rising main valve upon completion?

 

[anotherbgeng]

if your boiler is a combination boiler then shutting the rising main stopcock and opening the taps upstairs and down stairs will vent the pipework ,remember to fit service valves under the new tap assembly ,,,
switching the water back on will blow any air thru the hot water side of the boiler.....just ignore the isolation valve under the boiler

 

[Burnerman]

No, turn off the main stopcock, then do what you gotta do.
put isolators before your new taps - it'll give you less time with the HW off, and be much easier for you in the future.
John