The clearest gas line leak warning signs are a rotten-egg or sulfur smell, a hissing or whistling sound near a gas appliance or meter, dead or yellowing grass in a line over your buried gas line, and an unexplained spike in your gas bill. Physical symptoms like headaches, dizziness, or nausea that improve when you step outside are another red flag. If you smell gas, leave the house immediately without flipping switches, then call NW Natural's emergency line at 800-882-3377 or 911 from outside — and call a licensed plumber for the repair once the gas is shut off.
The Smell Test: Rotten Eggs Means Stop What You're Doing
Natural gas has no natural odor. Utilities including NW Natural add a chemical called mercaptan specifically so leaks are detectable by nose, and it smells unmistakably like rotten eggs, sulfur, or sometimes a skunk. In our experience running gas service calls across Tigard, Beaverton, and Hillsboro, homeowners often second-guess a faint whiff — assuming it's the garbage, a dead animal under the deck, or well water with sulfur. We'd rather roll a truck to a false alarm than have you talk yourself out of a real leak.
Here's a detail worth knowing: mercaptan can fade. If a leak has been seeping into soil for weeks, the soil can strip the odorant out, so a buried yard line leak may reach your basement with almost no smell at all. That's exactly why the other warning signs on this list matter.
Sounds and Sights Around Appliances and the Meter
A steady hiss, whistle, or soft roaring near your furnace, water heater, range, fireplace, or the meter on the side of the house means gas is escaping under pressure. That's a larger leak, not a nuisance one.
Look at your burner flames, too. A healthy natural gas flame is crisp blue with a small blue-green cone. Yellow, orange, or lazy flickering flames, soot marks above a burner or on the water heater draft hood, and a pilot light that won't stay lit all point to combustion or gas-supply problems. We see this constantly on 25- to 35-year-old furnaces and water heaters in the older Metzger and Garden Home neighborhoods, where dust and a partially blocked flue starve the burner of air. Incomplete combustion produces carbon monoxide — odorless, colorless, and far deadlier than the gas itself. Oregon requires CO alarms in homes with fuel-burning appliances, and we check for them on every gas job.
Outdoor Clues Most Homeowners Walk Right Past
Leaks on buried polyethylene or steel yard lines — the run from the meter to a detached garage, fire pit, pool heater, or outdoor kitchen — rarely announce themselves indoors. Instead, look for a distinct strip or patch of dead, yellowed, or stunted grass over the line while everything around it is green. In wet Oregon winters, watch for bubbling in standing water or puddles, or a patch of lawn that stays oddly dry and dusty because escaping gas displaces soil moisture. We've located leaks in Tualatin and Sherwood backyards using nothing more than a combustible gas detector and a homeowner pointing at a three-foot brown streak in the lawn.
Your Gas Bill and Your Body
Compare month over month and against the same month last year. A 20% or greater jump with no change in weather, occupancy, or appliances is worth investigating. A slow leak wastes gas 24 hours a day, and it shows up on paper long before it shows up in your nose.
Pay attention to how you feel, too. Headaches, dizziness, fatigue, nausea, eye and throat irritation, and unusually sleepy pets are all consistent with low-level exposure. The telltale pattern: symptoms ease within an hour of being outside or at work and return when you come home.
What to Do — and What Never to Do
If you suspect a leak: get everyone and pets out, leave doors open behind you, and do not touch light switches, thermostats, appliances, garage door openers, or your phone inside the house. Don't light anything. Don't start a car in an attached garage. A spark is all it takes. Once you're a safe distance away, call the utility or 911, then arrange repair.
In Oregon, gas piping is not a DIY job or a handyman job. Any new line, extension, or repair requires a licensed contractor pulling a permit, and the system must hold a pressure test under inspection before it's approved. Our licensed techs handle leak detection, repairs, appliance reconnections, and new runs for ranges, BBQs, fire pits, and generators — see our gas line services for details on testing and permitting.
Smell gas, hear a hiss, or spotted dead grass over your yard line? Get out first, call the utility, then call Hydro Plumbing at (971) 241-2628. We're licensed (CCB #254405) and serve Tigard, Beaverton, Hillsboro, Lake Oswego, Tualatin, Sherwood, and communities throughout Washington & Yamhill Counties with pressure-tested, permitted gas line repairs.