3 Ways to Insulate Septic Pipe

In certain climates, insulation is the only way to avoid frozen lines

3 Ways to Insulate Septic Pipe
In colder climates, be sure to provide adequate cover to properly insulate onsite system pipes against freezing. (Photo courtesy of Jim Anderson)

Interested in Systems/ATUs?

Get Systems/ATUs articles, news and videos right in your inbox! Sign up now.

Systems/ATUs + Get Alerts

In a previous discussion I indicated the best way to avoid freezing in septic lines is to properly slope and bed the piping. However, in the climate where I live, temperatures routinely fall well below zero for extended periods so there are situations where additional insulation must be applied.

Some of the applications that immediately come to mind include: a shallow house sewer line to a septic tank that passes under a sidewalk or path that is kept open for the winter; sewer lines between multiple sewage tanks, such as septic tanks in series or septic tank to pump tank or media filter; where the supply line runs from a septic tank under a driveway or other area where topography or soils limit the depth the pipe can be buried; and last but not least, sewer connections out of mobile homes (How often do you have to crawl under a mobile home to thaw the pipes?).

I am aware of three ways to insulate pipe. One is to sleeve the sewer pipe in a larger pipe creating air space between the pipes that acts as insulation. This approach is one I see when I am out West or in the South where periods of freezing last only a few days at most. In my part of the world this would not provide adequate protection.

Another way to insulate pipe is to cut sheets of insulation, and lay them over the top of the pipe and along the sides. If this is done, it is important to use sheets of insulation rated for soil burial. Use of indoor insulation or attempting to wrap pipe in insulation batting will not be effective. Those products absorb moisture which makes them ineffective in soil environments. In addition, there is always the question of whether the sheets stay in place when back-filling. There is no guarantee soil and rocks will not move the insulation.

My preferred way is to use pre-insulated pipe where a urethane foam surrounds the pipe and this is encased in a polyethylene sleeve. This eliminates concern about movement of the insulation and creates a consistent sewer line in the area where insulation is needed. Over the years I have seen several products like this; it may take a little work to find a nearby supplier, but it is well worth the effort in reducing time of installation and future headaches.  

I would be interested to hear from installers who have used these methods about their effectiveness for specific applications.

About the Author

Jim Anderson is connected with the University of Minnesota onsite wastewater treatment education program, is an emeritus professor in the university’s Department of Soil Water and Climate, and is involved with the National Association of Wastewater Technicians.

Send him questions about septic system maintenance and operation by email to kim.peterson@colepublishing.com.


Comments on this site are submitted by users and are not endorsed by nor do they reflect the views or opinions of COLE Publishing, Inc. Comments are moderated before being posted.