Where to find gas leaks

The one home inspection item that consistently causes home buyers to 'freak out' more than anything else is a gas leak. Believe it or not, small gas leaks are actually quite common at old houses, and they're usually simple for a plumber to fix.

Today I'll share the most common locations for gas leaks, and I'll share my home inspection techniques for finding gas leaks in old Minneapolis and Saint Paul homes.

The most common place for me to find gas leaks is at gas valves. Older style gas valves that aren't allowed any more today are often referred to as lube valves or plug valves. If you have a Truth-in-Housing Evaluation performed in Minneapolis and the evaluator marks down "old gas valves" or "unapproved gas valves", this is what they're referring to.

These valves are easily identified by a nut or spring on the valve across from the handle; newer gas valves don't have these. I would estimate that I find leaks at about one out of every five of these valves. Gate valves, which should only be used for water, are also common offenders.

The repair is always simple - replace the the valve. In Minneapolis, if the appliance being served by an improper valve is replaced, the valve must be replaced at the same time. The second most common location for gas leaks is at unions. A gas union is a fitting that provides a disconnection point for a gas appliance. If the union doesn't get tightened enough, it will leak. Notice the bubbles in the union below? That's a small gas leak.

Flare fittings are the last common offender. Here in Minnesota, soft copper gas tubing is allowed just about anywhere, but it takes a little more skill to properly install soft copper than other types of gas piping. For a flare fitting, copper tubing gets flared out at the end and connected with a flare nut. If this connection gets bent or isn't tight enough, it will leak. For the record, that nut pictured below isn't the right type of nut for a gas line... but it's what I had sitting in my parts drawer as I was writing this blog.

To find these gas leaks, you can usually rely on your nose. If I smell a gas leak and nobody is around, I'll run around the fittings with my nose right up the gas line. This is a fast way of figuring out exactly where a leak is coming from. The only problem with this method is that I look very silly doing it. When I'm inspecting a house and my clients are with me, I use a combustible gas detector.

The problem with using a combustible gas detector is that they're ridiculously sensitive, and they'll often give false positives. For instance, if there is fresh pipe dope at a fitting, the gas detector will go off. When one finds a leak with a combustible gas detector, it needs to be confirmed by using a gas leak detection solution; it's a liquid that does about the same thing that dish soap would - it bubbles if there's a leak.

To make it easier for the repair person coming in behind me, I also mark the location of the leak with orange electrical tape, and I write "Gas Leak" on the tape, along with an arrow showing exactly where the leak is.

I've heard stories about appliance connectors leaking, but I've never found one that leaked. Next week I'll talk about defects with appliance connector installations.

Reuben Saltzman, Structure Tech Home Inspections - Email - Minnesota Home Inspector