Here's the background...This is up at my cabin, and from the beginning when we bought the place it was a little orange. I'd always turned it to the lowest setting when we weren't there rather than all the way down to pilot only, simply as a safeguard against possible freezing

Fast forward to the middle of last winter when I discovered it was not lit on a trip up there.

Upon inspection I found the FTR (Fixed Thermal Release) had popped & the inside of the burner chamber was very sooty. I initially thought it had something to do with the amount of snow we had up there. Possibly covering the vent pipe on the roof & suffocating the flame.

I replaced the FTR & cleaned out the burner & innards of soot. I put it all back together & fired it up only to find it was burning more orange than I'd ever seen it. I decided to let it run for a while to see if it would clean up at all. After letting it run for about fifteen minutes I started hearing a slight sizzling and popping sound. I shut it down until I could figure it out so I wouldn't have to replace the FCR again.

I didn't tear into the vent pipe through the roof yet, though that may be my next step.

As a side note, the stove & furnace also use propane & burn a beautiful blue, as expected.

The water heater & furnace both share the same vent pipe & are located in adjoining closets. I'm experiencing none of these issues with the furnace.

My neighbor up there installed it in 2016 for the woman who owned the place before us. He says he's positive it's set up for propane & that's not the issue.

Is it possible something got into the vent pipe & is choking the water heater, or is it something else I haven't considered?

I'm a little befuddled by this, so any light you all could shed on it would be greatly appreciated.

Thanks for the help.

Why is my gas burning Orange

The flames from a natural gas stove can tip you off to a possible hazard. If you see orange flames instead of blue flames, the burners may need cleaning or adjusting. The orange color alerts you to your gas stove's improper combustion, which may emit unsafe levels of carbon monoxide gas.

Combustion Principles
For complete combustion to occur, a gas stove must supply the proper amount of fuel that mixes with the correct balance of oxygen, which yields carbon dioxide, or CO2. But when the fuel-oxygen mixture is imbalanced, combustion is incomplete and carbon monoxide, or CO, is the byproduct. The flame color is proportional to the heat intensity -- hotter flames, which result from the proper fuel-oxygen ratios and which achieve complete combustion, are blue. When the fuel-oxygen mixture is imbalanced, however, cooler pockets are produced in the flames because the fuel is not consumed properly. The result is orange flames.

Orange Flames
An imbalance in the fuel-oxygen mixture can have a variety of causes. Gas burner orifices may become clogged from a buildup of soot, which results in an uneven supply of fuel to the burner. When the flame burns the soot, the resulting incandescence is orange. The wrong orifice may be installed for the type of gas you are using; liquid propane and natural gas do not have the same air-to-fuel requirements. The air shutter might be sized improperly or might be damaged, preventing the correct amount of oxygen to mix with the fuel. With an insufficient oxygen supply, only some of the gas can ignite in a hotter blue flame, and the rest is wasted in a cooler orange flame.

Red Flag
Carbon monoxide gas is a combustion byproduct. Gas stoves that produce blue flames are typically emitting safe levels of CO when used for normal cooking tasks. Orange flames, however, are a red-flag alert that elevated CO levels may be present. CO poisoning causes flu-like symptoms, such as headache, dizziness and nausea. In extreme cases, CO earns its name as the silent killer because it may deliver a lethal dose to unsuspecting victims through its colorless and odorless presence. Warning: A gas stove is not a vented appliance and should never be used for home heating. Even a blue flame emits some CO, which can accumulate to dangerous levels in the absence of ventilation.

Green Light
The solution to the problem begins with recognizing that an orange flame from a gas stove is a red flag. The next step is scheduling a thorough inspection by a qualified gas appliance technician. The technician may need to clean the gas burner orifices, adjust the air shutter or replace an improperly sized burner. Correcting an imbalanced fuel-oxygen mixture is not a do-it-yourself task. An important home-safety feature is installing monitors that alert you to unsafe CO levels.

Pilot Light Color Flame Safety

By Kirsten Sorenson

A pilot light on a gas-burning appliance should be blue. Another flame color, especially yellow, means the appliance's gas-to-air mixture is unsafe and needs to be checked.

Process
When natural gas burns, energy is released in the form of heat. Three things are required for this process to work correctly and safely in an appliance: a pilot light, the right amount of fuel, and the right amount of air, according to the Pacific Gas and Electric Company.

Blue Color
Appliances are carefully adjusted to provide the correct mixture of gas and air. A normal flame should be blue, steady and cone-shaped. The Riverside County Fire Department says a pilot or burner flame should be about 90 percent blue. Flecks of orange are okay, according to Pacific Gas and Electric Company. However, "if the flame is yellow, large, and flickering the appliance may need a safety adjustment."

Exceptions
Decorative gas appliances such as fire logs are designed to have a yellow flame.

Newer Appliances
It used to be that a pilot light burned constantly, but in some newer appliances, the pilot light is a spark that occurs only when you turn on the appliance.

Odor
A slight odor of natural gas means a pilot light may have gone out, according to the Pacific Gas and Electric Company.

Warning signs
If natural gas is burned without enough air, it may produce carbon monoxide, a poisonous gas.

The Louisville Gas and Electric Company says that a person exposed to carbon monoxide "may complain of dizziness, headache, nausea, fatigue and other flu-like symptoms."

I know our propane supplier has a trained, state-licensed, bonded tech that corrects problems like that, and that’s who I’d call if I was dealing with something similar.

You should have a draft hood over the top of the heater where the vent pipe starts and so if there was a problem (blockage) in the vent itself then the exhaust and soot would be spilling out.

Keep in mind when you are messing with these gas things you stir up dust and that can cause the flame to turn orange. But that is very temporary. I'm wondering since you said "mountain house" if the altitude the house is at may have something to do with it. Propane by nature is dirtier when combustion is incomplete... more carbon in its molecule... as you suspect, draft may be wrong or it may not be getting enough air to the burner. Probably best to consult an expert.. even though I've sometimes found the folks who sell propane aren not always such.

Photo of the data plate?

I called the gas company a year or so ago when our natural gas cooktop on our range was burning orange, rather than the expected blue color. The tech checked it out and then asked whether we were using a humidifier in the house.

As it turns out my wife had recently purchased a few of the newer atomizer style humidifiers, and the vapor they emitted were causing the orange flame. Remember the science experiments in high school with bunsen burners?

As it turned out, there was nothing wrong. The colored flame was due to airborne particulates, which evidently contained chemicals from our municipal water supply.

However, you always want to take precautions when something doesn't seem right.