Gas leak detection

If you can smell gas right now, put the phone down and go outside. Take everyone with you. Do not touch a light switch, an appliance, a garage door opener or a phone on the way out. Once you are outside, call the gas utility on its leak line, or call 911. A plumber, this one included, is the call after that one, never before it.

What it covers

Gas, not water. This page is fuel gas: the piping, the fittings, the shutoffs and the appliance connections that carry natural gas or propane through the house. If the problem is water appearing where it should not, that is leak detection, a completely different job with completely different equipment.

The work is turning a suspicion into a fact. Most people who call about a gas smell are not sure: it was there in the morning and gone by lunch, or one person can smell it and another cannot, or the detector chirped once. A pressure test on the isolated house piping either holds or it does not, and that single result decides whether there is a leak at all before anyone opens a wall or condemns an appliance. If it does not hold, the leak gets found joint by joint, repaired, and the whole run tested again.

It also covers the thing people often mean when they say gas problem: an appliance that is burning badly. That is a combustion fault rather than a leak, the two get confused constantly, and both get looked at on the same visit because both start at the same appliance.

Why it matters

Fuel gas only burns within a range of concentrations in air, which sounds reassuring until you consider what a small leak does in a closed basement or a shut up house in winter. It accumulates. The size of the leak matters far less than the size and the ventilation of the space it is leaking into, which is why a smell you noticed once and have stopped noticing is not evidence that it stopped.

The combustion side is quieter and in some ways worse. An appliance burning incompletely produces carbon monoxide with no smell and no warning, and the symptoms pass for a winter bug because they ease every time you leave the house and return when you come back.

There is also a plain practical argument. A leak found and proved is a repair to one section of pipe. A leak left alone is eventually found by somebody else, often during a sale or an insurance inspection, at the point where it costs the most and the schedule is not yours.

None of this is a reason to fear a gas appliance. Properly installed and properly tested gas piping is safe and boring, which is exactly what it should be.

Questions people ask

I smelled gas yesterday and today I cannot. Has it stopped?

Not necessarily, and the smell alone cannot tell you. A nose stops registering an odor it has been living with, a window opened for an hour clears a room, and a small leak in a large space may only reach the level you can smell at certain times of day. The only thing that settles it is a pressure test on the piping, which either holds or does not. Until that has been done, a smell you noticed once is a leak until proven otherwise.

How is a gas leak actually found?

Not by smell. The house piping is isolated from the appliances and put under test pressure, and watched. If the pressure holds, the piping is sound and the search moves to the appliances and their connectors. If it drops, the piping is worked section by section and then joint by joint, with an electronic detector and with leak solution on the fittings, until the exact joint is found. The repair is then one joint, and the whole run is tested again afterward.

The carbon monoxide alarm went off once and then stopped. Does that need looking at?

Yes. An alarm that sounded and cleared was reading a real level that then fell, usually because an appliance stopped running or a door opened. It will be back the next time the same appliance runs under the same conditions. The fuel burning appliances in the house are worth checking for how they are burning and how they are venting, because carbon monoxide comes from burning and venting faults, not from leaks, and a pressure test on the piping will not find it.

Can the gas piping in a house we are buying be tested?

Yes. A pressure test on the house piping tells you whether the pipe and its joints are sound today, and that is worth knowing before the closing rather than after. It does not tell you whether the piping is big enough for what you plan to add, or how each appliance is burning; those are separate questions, and the gas lines page covers the first one.