Turn off power or gas supply to the old water heater
Shut off the cold water supply
Drain the old tank completely
Disconnect water lines, venting, and electrical or gas connections
Remove the old water heater
Place the new water heater in position on a level surface
Install a drain pan if required
Connect the cold water inlet and hot water outlet
Install or reconnect the temperature and pressure relief valve and discharge pipe
Connect the venting system for gas units
Connect the electrical wiring for electric units
Connect the gas line for gas units and check for leaks
Open the cold water supply and fill the tank
Open a hot water faucet to release trapped air
Check all connections for leaks
Restore power or relight the pilot for gas units
Set the thermostat to the desired temperature
Test the water heater for proper operation