Turn off the power or gas supply to the old water heater
Shut off the cold water supply
Drain the old tank completely
Disconnect the water lines
Disconnect the power, gas, or vent connections
Remove the old water heater
Place the new water heater in position
Ensure the unit is level and properly supported
Install a drain pan if required
Connect the cold water inlet
Connect the hot water outlet
Install dielectric unions or approved fittings if needed
Connect the temperature and pressure relief valve
Run the relief valve discharge pipe to a safe location
Connect the power supply or gas line according to the unit type
Install venting for gas or tankless models if required
Open the cold water supply and fill the tank
Bleed air from hot water taps until water flows steadily
Check all connections for leaks
Restore power or relight the pilot as applicable
Set the thermostat to the desired temperature
Test the heater for proper operation
Dispose of the old unit according to local regulations