Fixit: Septic system can freeze; give it cover

Q Do I need to worry about the septic tank freezing at our cabin up north?

A Yes. When it's cold and there is little snow cover, septic systems can freeze. When cabins or homes are unoccupied for long weekends or extended periods, no sewage is entering the system to raise temperatures enough to prevent freezing.

To keep your septic system from freezing

• Place a layer of mulch (8 to 12 inches) over the pipes, tank and soil treatment system to provide extra insulation. It could be straw, leaves, hay or any other loose material that will not compact. This is particularly important if you have a new system that was installed late in the year and no vegetative cover has been established. (If your system is frozen, ignore this step, as it will delay thawing come spring.)

• Before leaving for an extended period, plan accordingly. Pump out your tank or arrange for someone to stop by and use the water regularly. If you live in an area with a high water table, pump out the tank only if it was designed for high water table conditions. If a shallow tank is left full for several winter months, the sewage will get very cold and may freeze. If you return home before temperatures start to rise, the effluent leaving the tank will be cold. If the tank is empty, you can start fresh with warm effluent. Pumping out the tank also may be a good idea if you use your cabin on a limited basis in winter.

• Use more water -- the warmer the better -- if the system is starting to freeze. For example, try spreading out your laundry schedule so that you do one warm/hot load per day, using your dishwasher and even taking a hot bath. DO NOT leave water running, as this will hydraulically overload the system.

• Fix any leaky plumbing fixtures or appliances.

• If you have appliances that generate very low flows, such as high-efficiency furnaces, you can put a heat tape in the pipe and then have someone come by to periodically run warm water. Alternately, you could install a small condensate pump that holds and discharges 2 gallons per cycle.

If your septic system is frozen

• Call a professional (one list is at septic.umn.edu).

Many pumpers and installers use steamers and high-pressure jetters to thaw septic system pipes. They may also add heat tape and tank heaters. Cameras can be sent down the pipes to determine where freezing is occurring and if repairs are needed. If the soil treatment system is full of ice, or there is evidence of leaking, don't bother trying to thaw the lines leading to the treatment area. The system won't be able to accept liquid until the area is thawed in spring.

What NOT to do

If your system is frozen, do not:

• Add antifreeze, salt or a septic system additive to the system.

• Pump sewage onto the ground.

• Start a fire over the system to attempt to thaw it out.

• Run water to try to thaw system.

For more information on septic tank use and care go to: septic.umn.edu, or call 1-800-322-8642.

Sara Christopherson and Ken Olson, Onsite Sewage Treatment Center, University of Minnesota Extension Service

Send your questions to Fixit in care of the Star Tribune, 425 Portland Av. S., Minneapolis, MN 55488, or call 612-673-9033, or e-mail fixit@startribune.com. Past columns are available at www.startribune.com/fixit. Sorry, Fixit cannot supply individual replies.