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How to Install a Propane Tankless Water Heater

This Old House plumbing and heating expert Richard Trethewey shows how to get hot water quickly and efficiently


1. Turn off the main water valve at the meter.

2. Cut into the existing water–supply pipes attached to the old water heater.

3. Remove the old water heater and mount the new tankless heater to the wall.

4. Run threaded iron pipe from the outdoor propane tank to the heater; tighten all connections with a pipe wrench.

5. Use a union fitting to connect the threaded gas pipe to the heater.

6. Run copper pipe from the existing water-supply line to the heater. Solder all copper connections.

7. Open the main water valve, and check your work for leaks.

8. Turn on the propane and plug the heater into a nearby electrical outlet.

9. Set water temperature to 120 degrees F at the heater's control panel.

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