Gas Leak or Debugging a House

| posted in: house  debugging 

For the past couple of weeks, we have been noticing a faint sour odor at times in the house. Usually located in the hallway between the living room and bedrooms. It was never very strong, nor was it persistent. It came and went. At first I didn’t say anything about it as I sometimes have olfactory hallucinations—I smell smoke when there isn’t any smoke. When I did mention it to my wife, she could smell it also.

Eventually I thought to do a search online. When I searched for “house smells like skunk” the results were filled with ‘Gas Leak’. So we called the gas company. The gas man came, and using a gas sensor found a leak where the gas feed line joins the junction where the gas lines splits to go to the furnace or the water heater.

We called the plumber, who came and redid the connection. The feed line is corrugated and he removed the last one or two rings and reassembled the joint. Apparently the nut compresses the corrugation so that it flattens and makes a seal. I watched him tighten the joint using a couple of large monkey wrenches; it isn’t coming apart any time soon.

Problem solved.

Or maybe not.

A day later I still caught a whiff of skunk-like odor in the same location in the house. Nuts. In programming one error often masks a second error. It seems that debugging a house is a little like debugging a program. Finding one error doesn’t mean you are done, it just means you stopped looking.

The second gas man did a more thorough inspection of the fittings and lines between our gas line and the water heater and furnace. He found two places where the meter beeped.

The first was the “drip leg” and the second was a junction between the flexible feed line and a 90° elbow near the water heater. The drip leg is a short length of pipe below all the other fittings, straight down from the incoming gas line. It is there to allow any debris in the line from construction to fall harmless out of the gas before getting carried to the mechanisms in either appliance.

The plumber came and discovered that the drip leg was no more than finger tight. It seems that the code inspection does a pressure test from the meter to the shutoff valves to the furnace and water heater. The code inspector doesn’t (I guess?) inspect the final couple of feet to the appliance. The plumber being thorough, took all the fittings apart, applied a new, generous amount of pipe dope, and refastened them all. The gas company, having been to our house twice in 3 days, requested a new air pressure test. The pressure test passed.

After turning the gas on and reigniting the water heater, the gas man ran his sensor over the whole affair one more time. It beeped again.

The problem by the water heater hadn’t been the junction between the flexible hose and the cast fitting, it was the fitting itself. When he applied some soap water to the elbow a tiny, tiny bubble appeared along one flange.

The plumber returned again, and replaced the elbow. Hopefully now we’ve found all the leaks and repaired them. Both my wife and I are still pausing here and there in the house to sniff critically to see if we detect an odd, sour, skunk-like odor. So far so good. The house is odor free.

Lessons Learned

The first error you find may or may not be the actual problem. It may be a cascade from the real problem. The first inspection on Sunday stopped when gas was detected at the junction between the incoming gas line and the fitting between the furnace and water heater. He was following the direction of flow for the gas and stopped at that point. The actual leak was lower, where the drip leg was. It may have been a false reading at the feed line junction.

The second lesson is to verify the information you’ve been given. Anecdotal information is good, but verifying for yourself is better. Had the plumber done his own test he might have discovered the lose drip leg or the faulty cast fitting.

The third lesson is to retest everything when you are finished with your repair / fix. (A) To ensure that you have addressed the problem that was presented, and (2) to make sure you didn’t create a new problem.

Lastly, don’t be afraid to call the gas company or police or fire department when something seems amiss. It’s their job to check things out. Everyone is happier in the end, and your house doesn’t go kablooey.

Author's profile picture

Mark H. Nichols

I am a husband, cellist, code prole, nerd, technologist, and all around good guy living and working in fly-over country. You should follow me on Twitter.