How do I install a septic tank under the permafrost, keep it from freezing in the harsh winter, what kind of piping and pipe insulation should I use?
Septic tanks contain bacteria that will break down septic sludge. These organisms will do much better in a warm environment than a cold one. There is some debate on how much insulation makes a difference when it comes to soil temperature and bacteria performance. However, a bigger concern is a septic tank freezing because it was not buried deep enough, or does not have enough insulation to protect it from cold air. A frozen septic is more likely in the winters of extreme cold with little snow. In that case, the ground freezes very hard and very deep.
When in doubt, it is cheap insurance to add a layer of rigid two-inch foam insulation on top of the tank and a few feet down on the sides. In fact, insulating a septic tank is a good way to use up all the damaged or left over pieces of foam from a jobsite. Another alternative is to have the top of the tank sprayed with several inches of polyurethane foam. Do not forget to consult with the Alaska Department of Environmental Conservation for the most recent codes for insulating a tank.