Inspection Training

How to Inspect the Exhaust Flue on the Water Heater (UPDATED 10/4/17)

While the inspector is at the water heater the exhaust flue should be inspected for any damage. The inspector will also want to make sure that it is properly installed and slopes properly. Please review the entire procedure below.


International Standards of Practice for Performing a General Home Inspection


3.6. Plumbing


I. The inspector shall inspect:

C. The water heating equipment, including the energy source, venting connections, temperature/pressure-relief (TPR) valves, Watts 210 valves, and seismic bracing.


II. The inspector shall describe:



III. The inspector shall report as in need of correction:



IV. The inspector is not required to:

B. Measure the capacity, temperature, age, life expectancy or adequacy of the water heater.
C. Inspect the interior of flues or chimneys, combustion air systems, water softener or filtering systems, well pumps or tanks, safety or shut-off valves, floor drains, lawn sprinkler systems, or fire sprinkler systems.

Axium SOP Differences

Axium Requires: Same as NACHI Standards of Practice.


Tools Needed

No tools required to inspect the exhaust flue.



  • While inspecting the water heater the inspector should check the exhaust flue for any damage and make sure that it is terminating to the exterior of the property. There is one picture required for this section and it should show as much of the exhaust flue as possible.

Common Defects

  • The exhaust flue contained possible asbestos or did not have proper clearance from combustible materials.
  • The exhaust flue had an excessive number of bends, was improperly configured, had inadequate slope, was not secured, or was separated.

Common Mistakes

  • Not checking the entire exhaust flue for damage from where it starts at the water heater to where it terminates outside of the property.

Report / Software


  • The gas-fired water heater exhaust flue appeared to be properly configured and in serviceable condition at the time of the inspection.


  • N/A


  • Electric: An electric water heater does not require an exhaust flue.
  • Not Present: This type of water heater does not require an exhaust flue.


  • The gas-fired water heater exhaust flue [word 1]. A qualified contractor should evaluate and repair or replace as necessary and according to current standards.
    • Asbestos
    • B-Vent Clearance from Combustible Materials
    • Excessive Number of Bends
    • Improperly Configured
    • Inadequate Slope
    • Not Secured or Separated