11 Rules for Venting a Tankless Water Heater (Gas)

As I discovered there are many rules as to where you can not install the exit of an exhaust vent for a tankless water heater. These, as much as any other criteria, really determine the ultimate installation location of the heater.
  1. Terminating an exhaust vent under a deck is not permitted - this is the one that really hurt us!
  2. 36 in (twin pipe installation) directly below or 12 in horizontally from an opening; operable windows, doors and any non-mechanical fresh air openings
  3. 24 in below a gutter, sanitary pipework or eaves or12 in where they are protected by metal shielding
  4. 12 in from any internal corner or external corner
  5. 12 in above ground or snow pack
  6. 7 ft Above a paved sidewalk
  7. 24 in from an opposing wall or structure facing the vent termination
  8. 60 in from the relief valve of a gas regulator
  9. 48 in from a vent terminator facing another vent terminator or 60 in vertically between two exhaust vent terminators on the same wall or 36 in Horizontally between two exhaust vent terminators on the same wall
  10. 36 in horizontally and vertically from combustion air inlet of a twin pipe system
  11. 6 ft From the gravity combustion air inlet any other equipment