I think everyone should have a few SharkBite fittings in their plumbing box; they can come to your rescue in the right situation.http://www.cashacme.com/prod_sharkbite.php
A few weeks ago I had a zone valve fail, and I had to cut into the system to sweat in a new zone valve. I closed the isolation valves (old gate valves), and cut the zone valve out. I then discovered the old gates valves were leaking by, and the water wouldn't stop dripping. I couldn't sweat the connection with the dribble of water coming out of the pipes, and with the subzero temperature outside, I didn't want to drain the entire boiler. I had two SharkBite shutoffs on hand, so I sweated some copper stubs on the zone valve and installed it with the SharkBite fittings. The heat is back on, and I'm grateful that I had those fittings on hand.