Intermittent gas leak - is that a thing?

[Derek Daun]

I have a potentially small and intermittent gas leak in a house that's becoming a real pain. And before you immediately chime in with 'call the gas company right away', I already did that. That's why it's becoming a pain.

It started when I was getting ready for a city rental inspection when my inherited tenant casually mentioned that I should keep the fans in the kitchen on, as she uses them to keep away the smell of gas that has been coming and going since the stove was replaced 10 months ago. Apparently she didn't think it noteworthy to mention this to me before that. Would have been nice to know when it was installed, to have the installer/manufacturer deal with it. Anyway; I take a look, and don't smell anything, but tell her to call me next time it happens. A couple weeks later it happens again; she has the fans on when I get there, so I still don't smell anything. I call PGE (gas company) regardless. 

PGEs tech comes out, and makes a comment regarding 'what is it this time'. Apparently he's been out here before (I've only owned the place for a little over a year). He uses the sniffer around the range and find nothing. Leak tests the house - finds a leak at the meter (which is outside, and not close to kitchen) - but the house line looks sealed. Sniffed around the hot water heater -fine, but he does flag a cut in the plug gasket where the ignition assembly enters the combustion chamber. He says its an okay short term fix while waiting for the gasket part, but as the gas company, he can't leave the house with it like that. He says that wouldn't be the issue anyway, and he thinks tenant is simply leaving the knobs turned on the range.  Then he gets called out on an emergency call - so he turns the gas off and leaves for a couple of hours. 

I'm not there when he returns, but I understand he unhooks the gas line to the water heater, turns the gas back on, and inspects the stove some more. He tells her to use the hood, thinking she is just complaining about the gas you smell when you ignite the burners. As far as I know he didn't test the water heater with it actually ignited.

I ordered an OEM ignition system for the hot water heater, and in the meantime put some gasket sealant on the plug, and hooked it back up.

Well, 4 days later I get a call from the tenant saying the entire house smelled like gas again. I go over there right away. She has all the doors open with a fan running, but there is very slight smell of gas around the stove. I check for leaks everywhere around the range using soapy water, and get nothing. I notice the oven knob isn't completely in the off position, but that shouldn't matter since the oven gas (unlike the burners) is triggered by the thermostat current, not the knob position.

The tenant is a little flaky, but is generally competent in taking care of things, and would  know if she is leaving the range on. I also talked to the daughter when she was over, and she confirmed having smelled gas previously, and the first thing they check is the knobs on the range.

I assume if it was always leaking, the pressure check on the line would have caught it, so I assume it's intermittent. Any theories?

My thoughts:

• Something on the stove. Range burners seem unlikely since the mechanisms are so simple. Maybe the oven ignition system. The tenant seems to think it happens after she has used the range, so possible jostling the oven slightly opens the oven gas relay?
• Hot water heater. It's outside in a hot water heat closet, but it does butt up against the exterior kitchen in wall. It seems possible, but unlikely, that some sort of leak could be penetrating through the wall penetrations, and someway working it's way into the kitchen. A possibility of being intermittent could be if there is a leak between the line going from the ignition assemble to the burner. Then it would only leak when the water heater was on. Seems unlikely.
• Furnace is on the roof, so that seems very unlikely. 
• Tenant is going crazy. She has had some mental health history problems, and could be trolling herself with the gas burners.

[John Warren]

@Derek Daun sounds like a real pain! If you have other properties in the area, you might try pulling the stove and throwing a new one in there. It seems like the source might be the stove from what you are saying. I always like to try the simplest things first. 

[Derek Daun]

@John Warren. Switching the stove is a good idea. I had kind of considered it, but ruled it out as being to much of a hassle, but now that I think about it, it's going to be one of the next steps. This tenant is one of my charity cases, so I can justify swapping it with an older oven from a house with market rate tenants down the street.

[Dennis M.]

@Derek Daun

Find a new tenant

[Kevin Bazazzadeh]

@Derek Daun It can be difficult to determine the extent of a natural gas leak, as the mercaptans that it is spiked with can be detected at as low as couple of ppm. The sniffer you mentioned in the original post is likely a combustible gas detector. You can pick these up for a pretty cheap price online and test some points around the stove for yourself if you wanted to. Additionally a problem with metal lines, and why it may be intermittent, is that it could be due to thermal expansion/contraction. Basically, a line/fitting gets hot and expands, then it cools down and contracts and gives the gas a place to channel through. All that being said, if the problem started when the new stove went in - I would agree with @John Warren you may just replace it.

[Thomas S.]

Switch out the stove before you do anything else. The cause is either the stove or the tenant. Most likely the tenant is the problem. Typical of charity cases.

[Scott Mac]

Hi Derek,

If the stove moves at all, it might be the metal flex pipe that feed gas to the stove in the back.

Also maybe there is a gas pressure regulator on the house inlet feed that is malfunctioning.

If it were me and I smelled gas (and it wasn't immediately obvious where it was coming from),  I would evacuated the house and call the gas company immediately to come find it right then.

For tenant safety Home Depot sells "combination Carbon Monoxide and Natural Gas Alarms" that mount on the wall.

Good Luck!

[Derek Daun]

Quick update: I changed out the flex pipe just to make sure. Interestingly, after testing everything, I came back about 5 minutes later, and there was a gas smell around the burners that wasn't there when I had turned them off. This fits the description from the tenant, and points to a thermal expansion leak inside the piping going to the burners. Ugh, I can only imagine how difficult this will be to get the warranty to cover.

[Sam Hopkins]

@Derek Daun you can get a new range for like $400 delivered from HD.