In July 2003, a new federal mandate took effect requiring residential gas water heaters under 75,000 Btu to have a Flammable Vapor Ignition Resistant (FVIR) device. The idea was to prevent a small number of accidents that occurred every year, usually when someone used gasoline or solvents near the pilot light of a water heater.
Each manufacturer came up with its own system. Some worked better than others, and some worked very badly indeed. There were many cases where a water heater simply stopped working, and homeowners who had gotten used to water heaters behaving very reliably, were baffled and didn’t know what to do.
Most of the problems have now been solved, but there are many people now who hate a given brand of water heater, based on their experiences, and will never buy it again.
One of the new realities is that water heaters are no longer install-and-forget. They may need periodic maintenance merely to keep on functioning, such as cleaning air intake screens.