Flame too high...Thermocoupling? Thermostat?

Discussion in 'Water Heater Forum, Tanks' started by zian, Jul 8, 2009.

  1. zian

    zian New Member

    Jun 11, 2009
    In our cottage that doesn't get too much use in the winter monthes our LPG 30gallon hot water heater (that has not been used constistently for about 2 years).

    Yesterday during a bath a persons eyes started to burn. Checked it out quick and the source was the paint/coating on the exterior of the heater was being heated (aka burned) pretty darn bad. When the heater would kick in the flame would reach all the way outside the "firebox". Not good. Gas pressure too high?

    In past years I have replaced the thermocouple and I think I may have also replaced the whole burner assembly. It worked good after that for quite some time. No burning exterior tank etc.

    I just can't recall from the last time I replaced the thermocouple...With the gas off at the thermostat (gas still on at the tank outside) and there is no gas shut off between the lpg tank and the water heater. There is a pressure control valve between the lpg tank and the house/heater.

    With gas still running to the heater should gas leak when I remove the thermocouple from the thermostat? t does. I searched the net and these forums and could not find out for certain.

    The flames on our stove seem fine...not too much pressure?
    The water heater is not looking good.
    Could it be the thermostat on the heater?
    Could it be that pressure valve between the house and the lpg tank?

    Thanks for any help folks.
    btw...times or tough and money is an object.
    Unfortunately we can't be springing for a brand new water heater anytime soon. (Un)fortunately we are also pretty good at going without warm/hot water too. Heck we can even go without "running" water for years at a stretch ;) Good thing the cottage is on a lake.

    Thanks again.
  2. jimbo

    jimbo Plumber

    Aug 31, 2004
    San Diego, CA
    First, shut off the gas to that water heater before you have to appear on the 6 oclock news. SOMETHING is seriouslty wrong. The thermocouple performs only one function....it makes sure there is a pilot before allowing the main valve to turn on.

    It sounds like a main gas valve/thermostat problem. You need to have a qualified technian look it over.
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  4. kingsotall

    kingsotall Plunger/TurdPuncher

    Aug 17, 2008
    Hand copper part cleaned ready to go
    Flagstaff, AZ Sitting on an upside down 5 gallon b
    This is bad. Fork over some cash for a plumber. Or leave the WH alone. Shut gas off to unit and save up for plumbing service.
  5. zian

    zian New Member

    Jun 11, 2009
    I'm not messing with it.

    But just out of curiosity...
    (if gas is not shut off to WH) should the thermocouple connection to the thermostat leak gas when being disconnected?
    No safety cut-off type thingy there?
    I'm just wondering.

    I think it's time for a new water heater...this one has served us well for long enough.
    Thanks for the great advice.
    You won't be seeing me on the news ;)
  6. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Sep 2, 2004
    Retired Systems engineer for defense industry.
    New England
    Each gas appliance should have an individual shutoff. Don't know for sure about the gas and thermocouple, but remember, if you have a pilot light, it needs gas constantly, so there would be some coming out; just, not the main burner. This could be enough to accumulate and blow the house up. NG is light, and disperses (if there's room to escape), LPG is heavier than air, and accumulates in low places ready to explode. Under the right conditions, either can be deadly.
  7. zian

    zian New Member

    Jun 11, 2009
    Yes I have the On/Pilot/Off knob on the thermostat set to OFF (and that's gonna be where it stays). This cottage was built by Grandpa in the Mid 50's. The only shut off for the gas (that I can find) is at the big LPG tank outdoors.

    Sorry to be a PITA but....
    So if the Thermostat knob is set to OFF and with gas still going to WH and a man tried to replace the thermocouple would/should it still "leak" gas?

    put it another way....
    Say the thermostat works...gas line is live...thermostat set to off...disconnected main burner line, disconnected pilot line, disconnected thermocouple...would/should gas be flowing from the thermostat? from ANY hole?

    Of course....
    I'm not gonna do this (again) just wondering if it's a sign that the thermostat is toast.

    and...If it makes ya'll feel any better this WH WON'T be used again.
    I promise. ;)

    Thanks much everybody for your time and your responses.
  8. jimbo

    jimbo Plumber

    Aug 31, 2004
    San Diego, CA
    Most water heater valves these days....the pilot gas line will also cut off if the thermocouple is bad. That's why you have to press the red override button to light it. There should be NO GAS coming out of the thermmcouple connection. Don't confuse that with the pilot gas line.
  9. zian

    zian New Member

    Jun 11, 2009
    Thanks Jimbo,

    "There should be NO GAS coming out of the thermmcouple connection."
    That is what I was wondering.

    It's odd that the way too high flame seemed to come out of nowhere. Just glad we were home and around the bathroom at the time it started acting up. It could have been much worse.

  10. hj

    hj Moderator & Master Plumber Staff Member

    Aug 31, 2004
    Cave Creek, Arizona

    If a squirrel built a nest in the flue pipe, changing heaters will not cure your problem. IF the flue inside the heater is blocked, changing the heater will cure it, until whatever caused it to happen affects the new one also. Your symptoms do NOT have a single possible cause so you have to find out EXACTLY what is causing them, and fix it, instead of guessing at the cure. The burning paint is not the problem. The carbon monoxide gas entering the house IS the problem. And THAT will put you in the 6:00 news.
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