To install a water heater, the building must be equipped with a supply, a flue connection to vent out carbon monoxide and a cold water supply. To begin, you'll need to shut down the water, power and supply valve (if you're servicing an older, less-efficient heater). Drain the tank of water and use pipe wrenches to disconnect the line, then the water lines. Unscrew the exhaust vent from the top of the flue and remove the old water heater.

Put the new water heater in place, turning it so the burner and the controls are easily accessible. Make sure it is level by placing a level against the side of the heater. With Teflon tape, wrap the fittings for the cold water inlet and the hot water outlet, connect the fittings into the outlets, and tighten. Then, use flexible copper pipe to make the new water line connections. To connect the supply, use galvanized pipe with piping compound brushed on the threads to make the new connections.