re: OT Plumbers : question of soldering a water line

If the original work held for a year or more, it isn't necessarily bad workmanship that caused the leak. There is a lot of shite going on in a water line, especially one near a water heater.

If these are the flex lines connected directly to the water heater, you could have some code issues with using a sharkbite, or any kind of compression type fitting to make that connection. Sweating a connection is really easy, just make sure everything is cleaned up well with emery cloth, and use the flux. It's what lets the solder flow into the connection.

If you heat it up right, once the solder starts melting, you should be able to pull the torch away, and sweat the joint easy.