Hi. I enjoyed watching your youtube video. I’m from South Philly. You talk like I listen. Anyway…my fifty year old boiler and two zone system is making a very loud gurgling noise when the heat turns on. I suspect air in the pipes and want to purge them. I have watched a number of videos and yours was the only one that mentioned the fact that there may not be a zone valve. I have looked everywhere and cannot find the valves. There is, however a circulating pump like you said there may be. At long last my question; how do I switch it to manual so I can purge? Do I just ignore the “set valve to manual” step, turn off the water supply and drain, or is there something I must do with the pump? Thanks, in advance for your help.