bob haller wrote:

around here lots of people are using the flexible brite yellow gas
lines originally designed for gas dryers and gas stoves...

Yea - that's something I didn't think of.

Your water heater doesn't move around, shake or vibrate like a clothes
dryer does. The use of a short flexible link to connect a gas water
heater is a much safer application of those flex lines than any other
gas-using consumer device.