Weather Trends Point to Need for More Septic System Insulation

Declining snow cover in many areas should push you to consider several options to protect pipes and tanks against disruptive and costly freezing situations.

Weather Trends Point to Need for More Septic System Insulation

Jim Anderson, Ph.D., is an emeritus professor at the University of Minnesota Department of Soil, Water and Climate and recipient of the pumping industry’s Ralph Macchio Lifetime Achievement Award. Email Jim questions about septic system maintenance and operation at editor@pumper.com.

Aft the end of last winter season — which did not occur until after April 25 where I live, the last day we were able to ski and snowshoe — there were articles in papers and even television segments on how parts of Upper Michigan, Minnesota, and Wisconsin experienced more than the usual number of septic systems with freezing problems. This was attributed to the lack of continuous snow cover. Statistics were given indicating the trend has been for decreasing snow cover over the past 30 years.

The trend for the onsite industry means we need to question the need for insulating systems more than ever. During the years I worked in Minnesota, we relied on snow cover as a natural insulator to keep our “shallow” systems from having freezing problems. Now it may be prudent to consider insulating systems when they are installed to provide an extra measure of protection.

What needs to be insulated? Piping from the house to the tanks and from the tanks to the soil treatment area? The septic tank and risers?

FOR THE PIPES

I have indicated here and elsewhere that the best way to prevent freezing in the piping is for it to be properly installed and bedded to eliminate bends or bellies where water can collect and freeze when pipes are installed above normal frost depth. In pressure systems, the piping from the pump tank to the treatment area should be installed so it will drain back empty after the pump shuts off. This means no check valves and a weep hole in the pipe inside the tank for the effluent to drain into the tank.

A practice with a dual purpose is to provide clean-outs for the piping. This provides access points to remove solids if they plug the piping and provide access outside the house to thaw piping when necessary. One of the biggest problems mentioned in some of the articles was the lack of a good access point to get at frozen areas. Having the homeowner wait until spring for the system to thaw is not a good option, and excavating pipe in the middle of the winter is no picnic. I have friends with a bar in northern Wisconsin who had to close for eight days while piping from the bar to the tank was excavated and thawed. This was very costly at one of the busiest times of the year.

There are four ways to provide insulated piping.

Pre-insulated pipe is available and can be purchased through your pipe supply company. It usually consists of a smaller-diameter pipe inside a larger pipe with foam insulation filling the void between the pipes. In the past, I have talked about using this pipe if the piping is to run under a driveway or other high-traffic surfaces.

In a similar way, a smaller pipe inside a larger pipe will provide a good air-insulation pocket. This may be effective in areas where frost depths are shallower and winter weather is less severe. It is not as effective in colder areas of the Upper Midwest.

Installing sheet insulation over the top of the piping and/or on the sides to form three sides of a box can be very effective. If the insulation is installed only over the top, it must extend far enough to the side to intersect with a line from the bottom of the pipe extending at a 45-degree angle. This prevents the frost from coming around the side of the pipe.

Flexible insulation used to wrap around pipes is easier to use than sheet insulation. In all cases, the insulating material should be rated for burial and resistant to uptake of moisture from soil. If not, it will become saturated with water and lose all insulating value.

FOR THE TANK

For sewage tanks — including septic, pump and advanced pretreatment units — tank walls, lids, and risers may all require insulation.

In the past, a tank with a cover of at least 2 feet of soil was not thought to require insulation. In Minnesota, tanks with less than 2 feet of cover require insulation. This was based on data collected during winter months in Minnesota where the soil combined with snow cover help maintain tank temperatures necessary for biological activity (above 40 degrees F). The most critical time for the tank temperature was in the spring when the soil began to thaw and the snow was melting.

If there is less snow cover and melting occurs earlier during the winter, there can still be extended cold periods. Remember that it only has to be 32 degrees F for water to freeze. Additionally, for advanced pretreatment units to operate properly, the temperature must be higher than the biological minimum of 40 degrees F. So insulating tanks makes a lot sense in many situations.

To protect tanks, insulation board can be placed over the top and along the sides. Risers can be insulated by wrapping flexible insulation around the outside. If the riser is over a smaller opening in the tank, insulation can be placed inside the riser covering the smaller opening.

Available spray-on insulation materials can be applied during installation. These products have a secondary benefit in terms of providing additional sealant for any tank seams, either at the cover or at midtank. The tank must be properly sealed and watertight for the insulation to be effective. Just as with piping, this insulation must be suitable for burial.



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