Possible gas leak?

[Chris Branscome]

Our water heater is in our utility room. Last night, we could smell gas in the utility room. It wasn't overwhelming, but definitely noticeable. The pilot light on our water heater was still on, and we were getting hot water. Just to be safe, I shut the heater off and turned off the gas supply to it.

This morning I vacuumed the dust off of the thermostat and fittings, turned the gas back on, re-lit the pilot light, and sprayed soapy water on everything. I couldn't see any bubbles anywhere. It's been back on for an hour now. It's heating water just fine. Puzzlingly, there's no gas smell. Our water heater is 15 years old, which (I think) is longer than the usual life span. What would you recommend? Should I replace it just to be safe? Keep using it for now and stay alert for leaking gas? Thanks in advance!

 

[Terry]

It sounds like you did well with your testing of the pipes. Where do I want to go with this? 15 years is old and at some point I would consider replacement. I prefer to replace on my schedule and not to wait for the leak to happen. Most of my gas water heaters last about 15 years plus or minus. I don't really know why you would smell gas one day and none the next.

 

[Sponsor]

 

[Chris Branscome]

Is it remotely likely that it attempted to go through a heating cycle last night and the gas simply failed to light? Or is there a possibility that any of the knobs on the thermostat are slightly loose, were leaking a little, and that by my moving them around I (temporarily) sealed the leak?

 

[Jadnashua]

If the mixture is off and there is a wind outside, you might smell a little gas prior to the main burner igniting, but it's also possible the shaft on the valve was leaking slightly, and moving it helped.

There is a very fine line between a non-combustible concentration and one that goes boom...you don't want gas leaks. The additive they put into the gas supply means that most people with normal smell capabilities will notice it prior to the concentration being high enough to be dangerous, but you wouldn't notice when asleep, or be there all of the time, or if the room is sealed so you don't smell it until you open things up.

 

[DIYorBust]

Sometimes a gas detector can find small leaks that are hard to see with the gas solution. If the gas was off overnight, it may take time to build up to a smellable concentration again depending on ventilation and other factors, but it's worth tracking this down in my opinion.

 

[Dana]

An atmospheric drafted water heater backdrafting during an ignition cycle could result in a bit of residual gas smell in the room, but it normally wouldn't persist for hours though it might if it were backdrafting a bit during part or all of the burn cycle.

When a clothes dryer is running and the door to the room is closed it depressurizes the room relative to the outdoors, increasing the backdrafting potential.

Try turning on all the exhaust fans in the house, turning on the dryer, and test at the draft hood for backdrafting (when the burner isn't active) with a smoke pencil or punk. Try a few configurations, door to the utility room open/closed, HVAC air handlers running vs. off, etc. Outdoor wind direction and speed can also play into backdrafting risks, but those factors are harder to control for the test.