Can I run a gas hot water heater on propane?
I have done the conversion many times, in fact if you have the paperwork your water heater came with the orifice to change it over may be in there. On the water heaters, furnaces and ovens/ stove tops I have done all that was needed was a small brass orifice . The orifice is a brass disk with a tiny hole and usually a number or letter stamped on it. The orifice is on the output side of the regulator and changes the amount of gas the pressure was the same with both propane and natural gas. If your’s did not come with the orifice your local plumbing and electric specialty store may have them that’s where I got them several times. I would check with the manufacturer to make sure your water heater can be run on propane but all it has taken in the dozens I have done was the larger orifice.