I'm replacing the water diverter in the hall bath. To do so, I have to cut the existing copper pipes (Which have no direct shut-off valve attached) and sweat on new ones. I've turned off the water shut off at the front of the house, not at the street, the hot water outlet on the water heater, and opened all the faucets, flushed the toilets etc.. The garden hose attachment at the water shut-off still trickles water in a steady stream. So does the existing diverter valve. Not much pressure, but could fill a cup in a minute. Is the system just bleeding? Because it doesn't seem to be letting off. Is there a vacuum back draining the water heater? Or is the main shut off not working?

The main shut off sounds like it needs a new washer. To drain the system, open the lowest faucet in the system and open up the highest one to break vacume. You do not need to drain the water heater. Good luck, tom