How to Install a Water Heater Shut-off Valve

In this video, This Old House plumbing and heating expert Richard Trethewey explains how to install a water heater shut-off valve.

Steps for Installing a Water Heater Shut-off Valve:

Turn off the water to the water heater.
Drain the water heater using an electric pump and garden hose.
Shut off the gas, then disconnect the gas line from the water heater.
Cut cold-water pipe leading to heater using a tubing cutter; repeat for hot-water pipe.
Disconnect flue from top of heater.
Lift heater, slide catch pan underneath, then set heater back down.
Reconnect gas line, after applying pipe dope to threads.
Screw the flue back onto heater.
Reconnect the hot-water pipe by soldering on a repair coupling.
Extend the overflow pipe with copper tubing down to catch pan.
Solder a copper union onto a threaded adapter; thread the adapter onto the automatic shut-off valve.
Solder a second threaded adapter onto the cold-water pipe.
Use tubing cutter to cut away enough cold-water pipe to install the shut-off valve.
Install shut-off valve to the cold-water pipe.
Plug sensor into valve; place float in water pan.
Turn the gas and water back on.
Test the valve by turning on the heater and manually raising the float valve; the heater should automatically shut off.