I recently bought a 15-year-old house in a development that is about 20 years old. Near the front corner of the lot is a plastic “Warning Gas Line” sign which is important if you plan on doing any digging in the area. I know what the sign means and why it’s there, but right next to it is a yellow tube with a white wire sticking out of it. Many, but not all of my neighbors have the same yellow sign and the same tube with a white wire. You can see the wire here.
Any idea what the wire is there for or what it’s connected to? I haven’t bothered to call the gas company yet to ask them about it…
The only reason I know this is: we are having an addition added to our house, including running new sewer lines.
The Inspector made a big deal about the position of the tracer wire, so I had to educate myself on the technology.
Ha! I mentioned somewhere around here that (in some parts of the world), gas pipes are made of plastic (so that they stretch instead of breaking when the ground moves). And was told that gas pipes are made from plastic coated steel. Well, I assumed that the poster was talking about American gas pipes, so I wasn’t bothered.
But it obviously bothered me enough that I feel vindicated to learn that American gas pipes *are * sometimes made of plastic, and need to be laid with trace wires so that they can be located.
It isn’t just gas lines that have tracer wires. Any underground line that’s not metal gets them. Sewer lines and sometimes water lines do as well.
If you’re going to dig up the ground with a backhoe or other powered equipment, there’s a number you should call first. Someone will then come out and mark the ground where any underground pipes are located. They even have a color code for the different utilities. (White = water; yellow = gas, and so forth.) They use the tracer wires to do this. At least that’s how it works around here, but I think this is common in most places.
The line to call for locates in the US is 811. Call before you dig–it’s a free service and it may save you some trouble. The color code that jjakucyk listed is correct, though cable TV will use orange and steam lines will use yellow.
Most gas pipes in the US for pressures under 60 psi are made of plastic, usually MDPE or HDPE (medium density polyethylene or high density polyethylene). That’s most distribution mains and services. Many utility companies are actively replacing steel and cast iron with plastic pipe. The pipe is yellow, or black with a yellow stripe, to match the locating color code, but a few years back you could have orange, pink, or black gas pipes. But it can’t be located like steel, so a tracer wire must be buried with it.
The main advantage is that corrosion isn’t an issue and costs associated with cathodic protection are avoided. Not only do plastics stretch some, they also can be curved easily and snaked in some tight spots. Plastic can be joined by melting pieces and fittings together, using some special tools and techniques, and the joints are stronger than the pipe itself.
If a line is hit, crews can squeeze plastic shut to stop blowing gas, make repairs, and remove the squeezers, and the pipe will bounce back.
Higher pressure lines will be steel, though there are some new plastics that can be used for higher pressure.
The crews can place an active signal on the wire. I watched them do it next door. The city widened our street and during the process relocated some utilities. In my neighbor’s drive way was a 4" iron cover. They pulled it up and it had the coiled wire attached which just went down an empty pipe to the utility line. They hooked a small transmitter to it and walked the line with a signal detector. The worker told me it was more accurate then just detecting the wire itself. I think he said it gave them a depth reading also.
That was my father’s job at a major gas company - he kept the books and maps showing every pipe and connection across much of the state. Back before 811, he was The Man who handled all digging inquiries. I understand that older eastern US cities may have lost track of what various companies and contractors did in the past. It’s time to whip out the ground-penetrating radar.
The first job I ever had was working in the Estates Dept of a Council in Wales. My particular task was to take the maps of proposed new council buildings; schools, old people homes, etc and ask the various utilities to add their pipes and cables, then I would amalgamate them all for the builders. What a waste of time that was. This was in the 50s and a lot of those pipes were victorian; no one had any real idea where they were, so some junior (like me) would just make a guess that the gas main was ‘there’ and the sewer was ‘there’ etc.
The builders were always digging the darn things up and then they blamed me for getting it wrong.
Tracer wires are also needed for fiber optic lines. A lot of them are being installed now.
My brother worked as a locator for a telcom company. They had to do work at a local school campus where the contractor who had installed fiber lines a year or so earlier had done a very poor job installing the tracer wires. Many were located several feet away from the location of the fiber lines; some ended abruptly in the middle of a run, and sme seemed to have been skipped entirely. His company (& the school district) had a much tougher job making additions/modifications to that campus because of this. They urged the school district to file a claim with the original contractor about substandard work, but I don’t know if that was done.