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How to Replace a Direct-Vent Water Heater

This Old House plumbing and heating expert Richard Trethewey shows how to install a new water heater when there's no chimney

In this video, This Old House plumbing and heating expert Richard Trethewey shows how to install a new water heater when there's no chimney.


1. Turn off the gas supply to the water heater, and disconnect the electricity by unplugging the heater.

2. Close the ball valve to stop the flow of cold water into the water heater.

3. Attach an electric pump and garden hose to the drain valve near the bottom of the water heater.

4. Extend the hose outdoors, then open the valve and turn on the electric pump to siphon water from the heater's tank.

5. Open the hot-water faucets in the house to allow all hot water to drain back into heater.

6. Once the water heater tank is empty, turn off the pump and close the house faucets.

7. Use a strip of emery cloth to clean the hot-water copper pipe leading into the water heater.

8. Cut the hot-water pipe with a tubing cutter. Repeat Steps 7 and 8 to cut through the cold-water pipe.

9. Use two pliers to loosen the union fitting that connects the gas line to the water heater.

10. Carry the old water heater out of the house. Bring the new water heater into the house.

11. Next, wrap Teflon tape around the hot- and cold-water connections protruding from the top of the new water heater.

12. Thread a vacuum valve onto a brass water heater T-fitting, then thread the T-fitting onto the heater's cold-water connection.

13. Thread a ¾-inch copper fitting onto the heater's hot-water connection. Tighten the fittings with pliers.

14. Set the water heater into position, then solder the hot- and cold-water pipes to the water heater.

15. Directly below the cold-water shutoff valve, install a solenoid valve. Plug the solenoid's power cord into an electrical outlet and set its moisture sensor on the floor beside the water heater.

16. If the heater springs a leak, the solenoid valve will automatically shut off the water.

17. Reconnect the gas line to the water heater, tightening the connection with pliers.

18. Attach a power vent to the top of the water heater, then make the necessary electrical connections.

19. Join the exhaust port on the power vent to the existing vent pipe using PVC pipe and fittings. Glue together the parts with PVC primer and cement.

20. Plug the new water heater into an electrical outlet and open the valves for the gas and for the hot and cold water.

21. Run a continuous bead of silicone sealant around the water heater to trap any potential leaks.

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