Installation Checklist for Gas Water Heaters

In this article, you will find the installation checklist for gas tank-type water heaters with atmospheric venting. Find out more about location, venting, plumbing, electrics, and gas work.

According to the manufacturers of gas water heaters, a licensed technician or a plumber should install and service, following local and national codes, including manufacturer’s instructions.

Below is the installation checklist for gas tank-type water heaters that is using atmospheric venting to remove the products of combustion. The checklist applies to any water heater manufacturer and should be used only as a reference.

Rheem gas water heaterRheem


  • The best location for atmospheric vent gas water heaters is as close as possible to the hot water fixtures, gas piping, vent system, and electrical outlet.
  • The gas water heater must be installed indoors where the products of combustion are transferred outside.
  • Tank type heaters are installed in a vertical position, on the floor (level surface), and not directly on the carpet. Avoid installation in the bathrooms, bedrooms, and occupied rooms.
  • It is recommended to put the metal drain pan under the water heater.
  • The water heating unit should be protected from freezing, including piping.
  • Provide enough clearances from combustibles such as clothes, paper, boxes...
  • The room must be free of paint, aerosols, solvents, gasoline vapors, and other corrosive and flammable materials, also not exposed to excessive amounts of dirt, dust, lint...
  • The unit has to be accessible and provide enough clearance for maintenance and service.
  • Never run the unit if flood damaged.
  • Do not install an unapproved gas water heater in mobile homes.


  • The water heater must be vented outdoors.
  • Locate the unit close to the chimney.
  • The venting/exhaust system must be done per codes.
  • The size and material of the vents are according to the local codes and manufacturer instructions.
  • A draft hood must be installed appropriately with vent connectors securely fastened.
  • A flue baffle must be in the flue tube.
  • A vent pipe must be free of obstacles, kinks, damages, and changes in diameter.
  • A recommended venting system should have a minimum number of elbows and min. lengths.
  • Provisions for air intake must provide enough air supply and have sufficient size. Small enclosures and confined areas must have two permanent openings. The size of each opening depends on the total BTUH input.
  • Avoid installing the unit, so it gets the fresh combustion air from rooms with negative pressure.
  • The air for combustion and ventilation must not come from the corrosive atmosphere.

emergency plumber

Plumbing work

  • The water heater is designed for potable water heating, so install the piping made of the suitable material (CPVC, copper).
  • The TPR valve must be properly installed with the discharge line.
  • Piping and connections must be free of leaks.
  • The shut-off valve should be installed on the cold water inlet line.
  • The thermal expansion tank must be installed for closed systems.
  • The manufacturer recommends the installation of the mixing or anti-scald devices to reduce the hot water temperature.
  • Fill the water heater tank before installation.

Gas connections

  • The gas line must have a shut-off valve, ground joint union, and a drip leg.
  • The size and pipe material per codes/instructions.
  • The water heater must use the type of gas listed on the rating plate.
  • Check for the gas leaks and correct them if you find any.

Electric work

  • Electrical connections must be made per codes and manufacturer instructions.
  • Install the water heater as close to the 120 VAC as possible.


Find Trusted Plumbers & Get Free Quotes