The new American National Standards Institute (ANSI) standard governing flammable vapor ignition resistant (FVIR) water heaters has been in effect for less than a year, and plumbers around the country are still adjusting to the subtle differences found in the installation and maintenance of the units.
To meet the new FVIR standard that went into effect July 1, 2003, a water heater must be designed so it can't ignite vapors from gasoline (or other flammable fluids) spilled outside the unit. The standard covers conventional gas-fired atmospheric vented water heaters of 75,000 BTUs or less with 30-, 40- or 50-gallon capacities, but will eventually cover all residential gas-fired models by July 1, 2005. So what's the big difference with a FVIR water heater?