I was concerned about the weight of the petcock as well, and since I JB Welded everything instead of solder, I just added a lot of JB Weld to the surrounding area to help spread the load.
NOFly, yup that is just a garden hose fitting with a compression collar from Home Depot. The 1/4" copper tubing was from an ice maker kit and fit perfectly. The vent line exits to the rear of the tank, just under the rack. It does not actually tie into the middle coils, just looks like it