I've got a combi boiler installed about 9 months ago. The CORGI plumber kinldy teed off from the 22mm flow and return pipes and fitted push fit stop ends to the 15mm pipes, ready for connection to a radiator in an extension.
I don't want to drain down the system if I can help it. As such, could I get away with will the new radiator and feed pipes, fitting push fit couplers, releasing the pressure from the system and then, quickly pulling off the stop ends and pushing on the couplers? Would I need more inhibitor in the new circuit and am I risking air locks>
You don't get airlock problems with pressurised systems as much as you do with older systems. If it does airlock, turning off a few radiators will push the airlock through within seconds.
You can do as you said, but risk getting wet as there'll still be quite abit of pressure. If you drain the system then yes inhibitor should be added - if you don't and you're not soldering then new inhibitor wouldn't be required.
If you do use flux and solder, then the system will require draining and flushing.
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