Converting LP water heater to natural gas

[Nordic Home Inspection]

I came over a Ruud 30 gal LP gas water heater from 1957. The water heater was fed with natural gas. I know it is possible to convert a LP water heater so it can be used with natural gas, but wouldn't that be more expensive than buying a new one? And how can you tell if it have been converted or not?

[David Meiland]

Someone will come along shortly with a better answer, but here's what I know about the opposite condition: a NG appliance that is fed with LP will have a flame that is wayyy too large... so I would expect a LP water heater fed with NG to have a too-small flame. It may or may not burn well and it would heat more slowly. When you replace the orifices on an appliance, there is sometimes a way of leaving notice for the next guy, such as a check box on the tag.

[Nordic Home Inspection]

I guess that makes sense since natural gas is a lower pressure gas than LP...wonder what the converting cost is though. Anyway...it was awesome to see such a old water heater in great shape:)

[davidmcg]

Cost to convert depends mainly on the appliance and where you are in the country as far as market economics go. We converted a NG stove to use propane when we move to the rural area. At that time I had no idea how to do it so I took it to the guy here. He charged a whole $25 for the jets and re-adjusting the stove. When we dropped it off I had no diea how long he would have it. Got home and with-in an hour he called said it was done, the price and if we didn't make it by the end of the day there would be a whole dollar per day storage fee.

But, I question why you would even want to take the time and spend the money on such an old water heater. Sure it looks great now, but lets say you convert it. Thats X dollars for that process. But, then you install it and you leave for work or what ever and come home hours later to a flooded home. The cost damages and clean up from that will be higher than a modern water heater.

Water damage, it's not worth the risk to install a used water heater.

[Jim Katen]

I came over a Ruud 30 gal LP gas water heater from 1957. The water heater was fed with natural gas. I know it is possible to convert a LP water heater so it can be used with natural gas, but wouldn't that be more expensive than buying a new one? And how can you tell if it have been converted or not?

As I recall, converting from LP to natural gas is easy. You just replace a spring in the regulator valve and install a new orifice. I'm not sure about the other direction (from Nat to LP) because every LP water heater I've seen has a heavy cast iron burner instead of the thin stamped steel burners that you generally get with natural gas units.

With something that old, you might not be able to find the parts to make the conversion. In that case, you'd need a new control valve - not really a big deal.

If the thing has been in service since '57, and if the flames looked good, you can pretty much be assured that the conversion was made properly.

As for the old unit, it might have a monel tank. If that's the case, it'll probably say so on the outside somewhere. If it's monel, and if it isn't all calcified, it could continue to serve well for decades yet.

[inspector57]

It has been years since doing it but lots of appliances used to be shipped with both sets of jets and conversion instructions and the installer made the adjustments on the spot along with installing the correct tag.

the reason for the different orfice is the different heat value in the two different gases, Propane has much more heat value than the same quanity of Natural gas even at the same pressure.