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Replace a Water Heater in Seven Steps

A cold shower may be your first clue, or perhaps it is the wet garage floor. After doing a little home improvement troubleshooting, you have determined that your old water heater has given up the ghost and needs to be replaced. If you are reasonably handy, you can purchase a new water heater at your local home improvement store, and replace it yourself.

1. Determine water heater size and type. A forty-gallon tank is the most common, but if you have a large family and use a lot of hot water, you might consider replacing it with a fifty-gallon tank if you have room. Determine whether it is a gas or electric unit, and purchase the same type.

2. Shut off the water supply to the tank and shut off the gas or unplug the power cord, depending on type. Attach a garden hose to the drain valve and open the valve to drain the tank.

3. Unscrew and remove both the inlet and outlet water pipes with a wrench. If it is a gas unit, turn off the gas inlet valve and unscrew the gas line from the water heater. Remove the flue hat at the top of the tank that connects to the exhaust flue.

4. Remove the old unit and set the new one in place, oriented so that there are at least six inches of clearance and the controls are accessible. Level it using shims if necessary. If the new unit is taller or shorter than the old one, you will need to replace the water inlet and outlet pipes with flex tubing.

5. Install the heat trap fittings in the top of the new unit, blue on the cold side and red on the hot side. Use Teflon tape on the threads to ensure against leaks. Attach the flex tubing to the fittings. If there is no shutoff valve on the cold water supply side, install one.

6. Turn on the water and fill the tank. Open hot water taps in the house to bleed the air out of the pipes.

7. If it is an electric unit, plug it in and set the temperature controls. For a gas unit, connect the gas pipes using pipe dope on the threads. Turn on the gas and check for leaks using soapy water on the connections and looking for bubbles. Light the pilot light and set the temperature controls.

If you live in an earthquake zone, you should secure your water heater with straps. If the unit is in the garage and you experience cold winters, a water heater thermal wrap around the unit will help preserve heat.