How to convert an Propane water heater into Natural Gas? I have Whirlpool unit for LP. It has a regular valve with an adapter for LP. If I remove this adapter, will it then work? Is burner the same or needed to be replace? Is valve had to be replaced and will the thread be the same if IO reinstall the valve from my old Natural Gas heater that leaked?

Credendovidis

Actually that is not too difficult to do, but you require the advice of a specialist.
You have to replace the inserts in each burner that controls the air and gas content mixture.
Take the inserts out, and ask a specialist for the correct inserts.

Success !

NaturalGasMan

Well that is close to the correct answer, there is a step or two that you will need to do besides that. LP runs at a much higher pressure than NG. There for you will have to regulate the pressure differently. Depending on the regulator that is on the appliance if there is one or if there is one in line, it may have to be replaced, some have a spring in them and all you have to do is replace the spring. Some are even easier. On some models the cap just needs to be turned over. There is a different size plug that pushes further into the opening and thus creating more pressure on the spring. Natural gas into a hot water heater should be delivered at 6" wc to 7" wc (water column) 6.5" wc is appox. 1/4 lb psi. The pressure after the gas valve to the burner should be around 3 to 3.5" wc. LP runs in the 10 to 14 range. Make sure your pressures are correct.
The previous answer is correct as well. The Orifices will need to be replaced on the burner, on a water heater there should only be one. It will most likely be brass. If you can get the specs for that model you can drill out the orifice to work on Natural gas. Best bet is to buy one for that model. Very important to get it the proper size. IF your going to buy the orifice you might as well pick up a conversion kit if one is made for that model. (best practice) The burner will work for either fuels.