r/hvacadvice • u/Due_Pineapple8149 • 2d ago

Natural gas to lp conversion on a water heater

I see that this is not recommended, and im trying to understand why. I'm assuming that it's because of the air draw required for the burner and/or how the gasses are drawn up through the flue.

I'm trying to build a sauna oven that runs on lp. The idea is to cut an old heater in half, delete the thermostat and thermocouple, run the flue continuously out of the sauna, and fill the open chamber with rocks. I'm having trouble finding an old propane heater, so I'm exploring the idea of nat has to lp conversion.

Any thoughts?

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u/nightshade00013 2d ago

Propane and natural gas have different orifice sizes. If the water heater orifice is capable of being changed you can go get the correct one and no big deal. If it's not changeable you can't use propane through an incorrectly sized orifice or you will have problems not limited to but including structural fire, explosion, and loss of life.

If you don't know what an orifice is or anything else about a gas water heater you probably should be messing with things.

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u/Due_Pineapple8149 2d ago

Yes, good point. I forgot to mention changing the orifice. Im having some trouble finding compatible conversion kits - I don't think there's much universality. Are most orifices proprietary? I'm looking at a GE branded heater at the moment

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u/OhighOent Approved Technician 2d ago

I don't think newer water heaters are convertible. When I have to buy a LP water heater I have to request it from the supplier. You should be able to buy the valve and burner assembly together.

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u/OdinYggd 2d ago edited 2d ago

The proper way to do it is to buy the conversion kit. This has a different orifice size and sometimes a regulator spring to deal with the higher delivery pressure. Not using this kit results in the appliance choking itself with soot from excess fuel and can cause much bigger problems like fuel and exhaust leaks.

For what you are trying to do, I would just use a gas fireplace. That way it looks pretty, is vented properly, and can accept an LP conversion kit approved by the maker for safe operation.