Begin heater removal by turning off the gas or electricity to the heater.
Drain the heater (Fig. 2). Opening a hot water faucet will let air into the system.
On a gas heater, separate the vent pipe from the draft hood. It should lift off after removing the sheet metal screw that holds it. After making sure the pilot light is out, disconnect the gas line at the heater and cap it.
Next, remove the heater from its water piping. If connected with unions--removable threaded fittings--take them apart with a pair of pipe wrenches. Pipes without unions will have to be hacksawed off (Fig. 3). Or a pipe/tubing cutter will do the job. The old heater can now be taken away and disposed of at a dumpsite.