I have a condo in the South End, and I’ve been using these guys for years for both plumbing and HVAC. They’ve done basic repairs for me, installed a new tankless hot water/heater system, installed a new air conditioner, put in wifi thermostats, done loads of basic maintenance (changing air and water filters, descaling, etc.), and once or twice, made night time or weekend visits to address an emergency problem. They have been consistently professional and have done excellent work for me. Their techs are clean, knowledgeable, respectful of my time and property, and they show up on time. I trust them to be in my unit unsupervised, locking up when they leave. Plus, they have very good centralized records, so you don’t have to repeat everything each time someone comes out. As far as I’m concerned, these guys are the go-to shop for residential plumbing and A/C in Boston.