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How to Replace a Tank Water Heater

Ask This Old House plumbing and heating expert Richard Trethewey helps a homeowner replace a tank water heater

Replacing a tank water heater

  1. Shut off the water supply to the water heater and the gas supply.
  2. Drain the water heater by attaching a hose to the spigot at the bottom and opening the draw off valve.
  3. Break the galvanized flue line connection at the top of the water heater and the gas connections.
  4. Clean the copper piping for the hot and the cold connections at the top of the water heater before you cut them using a pipe cutter. It’s a lot easier to clean them beforehand.
  5. Remove the old water heater.
  6. Because of the new energy regulations, it’s likely the new water heater will be slightly larger than the old one. Take some measurements to make sure the new water heater will fit in the same place.
  7. Place the new water heater in its place.
  8. Dry fit the old gas pipe to the union. When you have the right fit, use pipe dope on the threads to make the connections. Then snug them up with a pair of pliers. (This step should be done by a licensed plumber)
  9. Measure, cut and dry fit the 3/4-inch copper pipe connections from the water heater to the hot and cold lines.
  10. Connect those pipes using solder and a propane torch.
  11. Measure out galvanized flue line, cut it using tin snips and make the connection using sheet metal screws.
  12. Measure and cut copper pipe for the pressure relief valve on the side of the tank water heater.
  13. Turn the water line back on and check for any leaks.
  14. Turn the gas line back on and check for any leaks by using a soapy solution around the connections. If there is a leak, you will see bubbles forming.