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How to Replace a Tank-Type Water Heater

In this DIY Smarts segment, plumbing and heating expert Richard Trethewey helps a homeowner be proactive about their home maintenance by replacing their existing tank-type water heater before it fails.

Plumbing and heating expert Richard Trethewey takes us on a house call to relieve a homeowner’s stress. With a 16-year-old water heater lurking in the basement, the homeowner is expecting it to fail at any moment, so Richard suggests they swap it out with a new unit.

How to Replace a Tank-Type Water Heater

Note: Tank-type water heaters, particularly those of the gas-fired variety, should be replaced by licensed pipefitters, and they should secure permits for the project.

  1. Locate and shut off the water valve. It should be within a few inches from the top of the water heater.
  2. Locate and shut off the gas valve. Most gas valves will have a line that displays the position of the valve. This line should be perpendicular to the pipe to ensure that the gas is off. Once the valve is shut, use a pair of water pump pliers to break the union fitting below the gas valve and disconnect the pipes.
  3. Attach a garden hose to the drain at the bottom of the old water heater. Run the hose to a floor drain if there is one, or attach it to a pump. Using a screwdriver, open the drain by turning the stem counterclockwise and let the tank drain.
  4. Choose two spots on the existing copper pipes to cut, making sure to cut them high enough for the new tank if it’s larger. Use the sanding cloth to clean up the pipes before placing the tubing cutter on the pipe. Tighten the tubing cutter onto the pipe and turn it until the pipe cuts, tightening every few revolutions. Repeat on the other copper pipe, as well.
  5. Remove the flue pipe from the top of the water heater and the chimney. Some concrete may break, but this will be repaired when the new flue is installed. Remove the old water heater from its location.
  6. Use a pipe wrench to remove the trim from the old water heater. Remove the copper pipe stubs from the top of the water heater and the gas pipe trim from the bottom at the electronic control.
  7. Carefully place the new water heater in its location. Make sure it’s level by placing a level on top of the heater and using shims underneath. Mark the new flue’s location on the chimney with a pencil.
  8. Apply pipe thread tape to the pipes sticking out of the top of the water heater, running the tape in a clockwise direction. Install the copper piping to the top of the water heater using a pair of water pump pliers to tighten the pipes in place.
  9. Apply gas-safe pipe dope to the gas pipes and reinstall them using pipe wrenches. Be sure to tighten them firmly to prevent leaks.
  10. Solder the new pipes to the existing water pipes using a gas torch, flux, and lead-free solder. Reinstall the vacuum valve in the top of the fitting attached to the water heater. Turn the water on and let it fill the tank.
  11. If necessary, chip away the chimney using the cold chisel and a hammer. Install the new flue using self-tapping screws and a screw gun. Mix concrete and use a trowel to patch the hole around the flue to ensure gas cannot make its way back into the home.
  12. Install an overflow pipe on the side of the water heater using thread tape and water pump pliers.
  13. Turn the gas back on and check for leaks. Set the water heater to the desired temperature.
  14. Date the water heater by writing the month and year it was installed on the side.


Richard installs a hot water heater (tank-type) with the help of a homeowner. Richard suggests replacing the old hot water heater with a new tank instead of opting to install a new combination boiler, as it’s the most cost-effective solution and a really simple replacement.

Richard suggests that once the new hot water heater reaches the end of its life, the boiler will likely be at the end of its life too. At that point, replacing both the boiler and how water heater with a combination boiler is the best solution.

Tools and materials are manufactured by Rheem Manufacturing, available at The Home Depot.


Find what you need for this project at The Home Depot