Wimpy Water Heater Flame

[SpeakEasy]

Twice in several years I've had an unexplained issue with the flame on my water heater. It happened most recently over the weekend. Here it is: I light the pilot, warm up the thermocouple, and turn the dial to "on." Instead of a whoosh of gas and ignition, I get nothing. Then, after a couple of tries, I get a really wimpy, yellowish flame. This is a problem because it produces a lot of hot smoke which comes up through the exhaust pipe. This exhaust is so hot that it can melt the ABS above the water heater. (The first time I experienced this I didn't notice it right away, and I did get a "wrinkle" in the ABS). After a while, or after several tries, things return to normal. There is nothing obstructing the burner tube. My LP tank has gas in it because all my other appliances work normally. I'm wondering if it is possible that some sort of bubbles might occasionally form in the LP tank from traveling down the road. Has anyone ever heard of such a thing? What could be causing my wimpy flames?

Anyone?

-Speak

[austinado16]

Not a gas bubble issue.

Yellow flame being incomplete combustion, so I'd be looking for either a partial blockage in how the flame gets fresh air into the burner tube (could have cob webs or a creature's nest or egg sack in there) or something going on inside the gas valve.

I've taken the gas valve apart in my furnace and there was rust and little chunks of stuff in there.  Needless to say, I wasn't getting a good flame.  The valves aren't really supposed to be taken apart, so if you go down this path, make sure to check it for leaks once reassembled.

It's strange that your yellow flame will melt the camper, but the normal functioning blue flame does not.

[PattieAM]

Don't know your make/model of water heater, but in looking in my Suburban water heater manual, it says under Maintenance - do not allow burner to burn with yellow flame, because sooting will occur.  If flame is yellow and has an erratic pattern, shut down unit and have repaired.

Pilot should fully engulf the tip of the thermocouple as illustrated.

Inspect your unit for soot - if present anywhere on the water heater, shut down and have unit serviced - soot is indication of incomplete combustion:
-check for obstruction in burner or flue box
-check screen in door to be sure adequate ventilation.
-check grommet on the gas inlet to assure tight seal.

Another thing to consider - your altitude - if above 4,500 feet - your water heater needs to be derated, otherwise you might have improper burning operation - Pilot outage caused by burner lift-off or sooting from a yellow burner may occur indicating the possibility of carbon monoxide.  You may also otice a lack of efficiency in heating the water due to incomplete combustion at the higher altitiudes.  Deration is 4 percent for every 1,000 feet above sea level....above 4,500 feet.  ONCE YOU RETURN TO A LOWER ELEVATION, your unit will need the deration reversed for proper operation.