August 21, 2012
One of our long-term construction projects involves a modest two-story log cabin. Now that the electrical work on the cabin is complete and it's passed inspection, the next step we're tackling involves installing a propane gas line to serve the cabin.
the ditch leading to the back of the cabin
In the old days, gas lines were installed using steel pipe, but that has a tendancy to rust out in twenty-years or so. Nowadays, the practice has evolved to using a special kind of plastic piping and purpose-designed fittings to convey the gas from the storage tank into where it will be used. When we originally built the dining hall, we used black pipe. And while a twenty-year lifespan isn't trivial, it's also only a fraction of the useful life of any sustainable building. The upshot is that we dug up the metal line, and replaced with a line that met current specifications. While we like to look for traditional ways to do things, this is one of those cases where the new stuff is notably better.
a special-use coupling
The new line consists of three major components: the two 90° bends at each end, and a length of yellow gasline piping. These three parts of the line are joined together with two special use couplings, one of which is seen in the above picture. The coupling we used goes by the modest name of "The Elster Perfection PERMASERT Non-Corrosive Mechanical Coupling." The key thing about assembling the couplings is to carefully cut a 45° chamfer to the ends of each pipe. With that in place, the pipes slid into the coupling with an ease that well deserves to be called "perfection" : )
The installation code would allow for us to just stand the 50 gallon propane tank we'll be using next to the cabin wall, but having seen‒up close and personal‒how fast a grass fire can make its way through the forest, we chose to locate the propane tank some 60' away from the cabin. Digging that much ditch was a non-trivial amount of work, but in the long run, I look at investing in the ditch as cheap fire insurance.
the end of the gasline farthest from the cabin
The propane end of the gasline is capped with the sort of valve that one uses to inflate a tire. The purpose of it here will be to test the gasline for leaks by inflating it up to 10 psi and checking to see that it holds that pressure for at least 10 minutes. After approval, the test fitting will be removed and the line connected to the regulator on the propane tank.
the end of the gasline where it enters the cabin
The end of the gasline that enters the cabin is a bit more complex. First the gas passes through a shut-off valve which will allow us to work on the gas line inside the cabin without having gas flow into the cabin. The pressure gauge is there so that the inspector can confirm the integrity of the line by seeing that it holds pressure. Once the inspector approves the system, the gauge will be removed and that part of the tee will be closed off with a plug.
The other thing I'd draw your attention in the picture is the yellow wire that's been taped to the outside of the gasline. This 12 gauge wire runs the length of the gasline and serves as a way for someone in the future to determine exactly where the gasline is buried. In this case, it's fairly obvious where the line goes into the ground, where it comes out of the ground, and that the line runs straight between those two points. In other situations, the routing of a plastic line isn't as obvious, which is why having a wire that one can energize and then trace across the yard using a metal detector is good practice for gas, sewer and water lines.