Switching propane gas valve to nat gas water heater

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by jbclem, May 9, 2008.

  1. jbclem

    jbclem New Member

    Messages:
    5
    I have an old propane water heater with a fairly new main valve. I'd like to find a good used water heater but propane water heaters are rare. There are some 2 year old natural gas water heaters available and I'd like to know if there is a reason that I couldn't use my newish propane valve in a water heater that was originally set up for natural gas.

    I'm assuming the burner assembly has a propane orfice so that would also be transfered.

    jc
  2. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    It is never permitted to convert a residential Ng water heater to propane. It violates the manufacturer's instructions, its AGA/GAMA listing, the National Fuel Gas Code, and any local plumbing/building code.
  3. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,270
    Location:
    Cave Creek, Arizona
    Lpg

    1. tbe burner connection on a LPG thermostat is a left hand thread.
    2. The burner in a natural gas heater is stamped metal, in an LPG one it is cast iron.
    3. The internal pressure regulator is set too low for LPG.
    4. The orifice may not be interchangable even if you disregard the above reasons not to do it.
  4. jbclem

    jbclem New Member

    Messages:
    5
    Sorry for the long delay in answering, hope someone is still watching...

    Thanks for giving the specific reasons against this idea. Since I have a working valve/burner combination, and it's the tank itself that's old and rusting out, I thought I could just switch tanks but re-use the valve/burner combination so everything would be correct, propanewise.

    Is the tank from a propane water heater different from a natural gas water heater tank...heavier gauge metal, larger burner area? I'm trying to understand specifically what the differences are that would make it unsafe to use a natural gas water heater tank with a propane burner setup. How about the thread where the thermostat/valve screws into the tank? Is that different/incompatible?

    John
  5. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,270
    Location:
    Cave Creek, Arizona
    Lpg

    The tanks are the same, the burner, pilot, and controls are different and it you go up two postings, my previous reply gives the answers to your questions.
  6. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    hj has given the nuts and bolts reasons. The LEGAL reasons are that a water heater is listed by AGA ( sort of like UL for gas) and any modifications not performed BY the manufacturer IN their factory violate the listing, thus making it illegal to use. Also, since the manufacturer specifically prohibits it, then do so also is a prima facie violation of plumbing and building codes, which require that all equipment is installed per its manufacturer's requirements.


    So, we are not just trying to give you a run around. There are legal reasons, and practical ( SAFETY) reasons why you cannot convert.
  7. MACPLUMB 777

    MACPLUMB 777 TROJAN WORLDWIDE SALES RP

    Messages:
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    Location:
    Houston, Texas, United States
    Water Heater Changeout

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