How to Replace a Tank-Type Water Heater

Note Tank-type water heaters should be replaced only by pipefitters who are licensed and have the necessary permits.

  1. Find the valve and turn it off. The valve should be a few inches above the water heater.
  2. Find the gas valve and turn it off. Gas valves are usually marked with a line to indicate the location of the valve. The line must be perpendicular to the pipe in order to turn off the gas. After the gas valve has been shut, break the union fitting beneath the valve with a pair of water pump pliers and disconnect the pipes.
  3. Attach a garden hose to the drain located at the bottom of your old water heater. If there is floor drainage, run the hose down to it or connect it to a water pump. Open the drain with a screwdriver by turning the stem in the opposite direction. Let the tank drain.
  4. Cut the copper pipes in two places if the tank is larger. Before you place the tubing cutter onto the pipe, use the sanding fabric to clean the pipes. Then, turn the tube cutter until it cuts the pipe. Tighten every few turns. Repeat the process on the second copper pipe.
  5. Remove the flue pipe at the top of both the water heater and chimney. The new flue will repair any concrete that breaks. Remove the old water heating system from its original location.
  6. Remove the trim from the water heater using a pipe wrench. Remove the copper pipe stubs at the top of the heater and the gas pipe trims at the bottom near the electronic control.
  7. Place the new water heater carefully in its place. Place a level over the heater, and use shims to level it. Mark the location of the new flue on the chimney using a pencil.
  8. Apply pipe thread tape clockwise to the pipes that protrude from the top of your water heater. Install the copper pipe to the top of your water heater using water pump pliers.
  9. Reinstall the pipes using pipe wrenches after applying gas-safe pipe glue. Make sure you tighten the gas pipes firmly to avoid leaks.
  10. Soldering the new pipes with the existing pipes is done using flux and lead-free solder. Install the vacuum valve at the top of the fittings attached to the water heaters. Fill the tank with water by turning on the tap.
  11. Chip away the chimney if necessary using a cold chisel. Install the new chimney using self-tapping screwdrivers and a screwgun. Pour preventing gas from leaking back into your home, mix concrete with a trowel and patch the hole surrounding the flue.
  12. Install the overflow pipe to the side of your water heater with thread tape and water pumps pliers.
  13. Check for any leaks and turn the gas back on. Set the water heater temperature to your desired level.
  14. Write the date of installation on the side.


Richard installs a tank-type hot water heater with the assistance of a homeowner. Richard recommends replacing the old water heater with a tank rather than opting to install new boilers, because it is the most cost-effective and simple solution.

Richard says that the boiler is likely to be in the same situation as the hot water heater when it reaches its end of life. The best solution is to replace both the boiler as well as the hot water heater by a combination boiler.

Raheem Manufacturing manufactures tools and materials, which are available at The Home Depot.


  • Permanent Marker
  • Plumbers’ sanding cloth
  • Shims
  • Plumbers thread tape
  • Various copper fittings
  • Concrete
  • Lead free solder
  • Flux
  • Vacuum valve
  • Self-tapping chimney screws


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