I was told that when converting from propane to natural gas, the hot water heater is the only appliance that simply changing out an orifice is not an option. They (hot water heaters) must be replaced. Is this true? It is a four year old 72 gallon Rheem. Thank you.
The appliance approval, control valve, burner type, and design all have to do with safe operation using one fuel or another. Safety dictates that today’s appliances must follow the factory engineering specifications. Few units are convertible today.
The control on a natural gas water heater is set at 6″ water column pressure. An LPG unit needs 11″. You cannot replace just the thermostat since the burner outlet on an LPG thermostat has a left hand thread to preclude interchanging them. So that is the reason you have to replace a water heater.