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According to many onsite professionals, a winter of cold temperatures and little snow cover can cause freezing of onsite systems. Even in a normal Minnesota winter, freezing can occasionally be a problem. Identifying and correcting a potential freezing problem is far easier than dealing with a frozen system. Here are a few common causes of onsite system freeze-ups.
Snow serves as an insulating blanket over the septic tank(s) and soil treatment area (trenches, drainfield or mound). Snow helps keep the heat of the sewage and the geothermal heat from deep soil layers. Lack of snow allows frost to go deeper into the ground, potentially freezing the system.
Compacted snow will not insulate as well as uncompacted snow. Driving any type of equipment over the system compacts snow and sends the frost down deeper. Automobiles, snowmobiles, ATV's, foot-traffic, and livestock should stay off the system all year long but especially in the winter. Any time traffic over a sewer pipe, septic tank, or soil treatment area is anticipated, insulated pipe should be used.
Areas that have compacted soils such as driveways, paths or livestock enclosures tend to freeze deeper, affecting septic system components that may be in the area.
This often occurs in new systems installed late in the year where a vegetative cover could not be established before winter. The vegetative cover insulates the system and helps hold snow.
When homes or cabins are unoccupied for long weekends or extended periods of time, no sewage is entering the system to maintain sufficient temperatures to avoid freezing. This can also occur when very low volumes of sewage are being generated. In cases when only one or two people are living in a home, they may use only a small percentage of the designed flow for the system. This low usage may not be sufficient to keep the system from freezing. Frequent use, warmer water temperatures and greater water use are all important in cold temperature stress situations.
When a fixture such as a toilet or showerhead leaks, it sends a small trickle of water to the system. The slow moving and thin film of water form caused by trickle flow can freeze within the pipe and eventually cause the pipe to freeze solid. Appliances such as high efficiency furnaces and humidifiers can also cause water to freeze in the pipes due to the small amount they discharge.
A common cause of freeze-ups are sewer pipes and pump lines that are not installed with proper fall (change of elevation), or pipes that settle or sag after installation. Any time a dip or low spot occurs in a pipe, sewage can collect and freeze. Pump lines can develop a dip right next to or above the septic tank as a result of backfilled soil settling from the excavation during the tank installation. All sewage needs to drains out of the pipe from a pump line.
Open, broken and uncapped riser or inspection pipes and manhole covers allow cold air into the system and can cause the system to freeze.
If a system was hydraulically failing (e.g. water coming to surface or seeping out the side of a mound) it is a prime candidate to freeze. This effluent will freeze and prevent further effluent from entering the soil.
If your septic system is frozen, your first step is to call an onsite professional. Unless the cause of freezing is corrected the system will refreeze next winter. If you have a pump and hear water constantly running in a pump tank (a possible indication of a frozen system) shut off your pump and call an onsite professional. This will likely be a pumper or an installer who can help determine the cause of the problem and offer solutions. The University of Minnesota Onsite Program web site is one place to go to locate a professional - http://septic.umn.edu . Many pumpers and installers have devices called steamers and high-pressure jetters to try to unfreeze system piping. Other methods used to help fix a freezing problem include adding heat tape and tank heaters. Cameras can be sent down the pipes to determine where the freezing is occurring and if repairs are needed. If the soil treatment system is full of ice, or there is evidence of leaking, there is no need to thaw the lines leading to the treatment area, as it cannot accept liquid until the area is thawed in spring.
If it is not feasible to correct the problem or equipment is not available in your area, the only other option is to use the septic tank(s) in the system as a holding tank until the system thaws naturally. You will need to contact a pumper who will empty out the tanks when they are full on a regular basis .This can be very costly, especially with normal volumes of water use (50 to 75 gallons per person per day). Reduce water use by limiting the number of toilet flushes, taking short showers, using the dishwasher at full capacity, limiting running water to get hot or cold and doing laundry at a laundromat. It is smart to find the cause of the freezing problem so that it can be addressed in the spring, preventing future freeze-ups. Then preventative measures can be added to the system such as adding insulation around the tank and pipes or adding additional cover.
There are many misconceptions about how to deal with a frozen onsite system.
Depending on your system, location, and water use, you may never have a freezing problem. However, there are several steps that you can take if you are concerned about your onsite system freezing. Here are some precautions if you have had a past problem or are concerned about having a future problem. It is not necessary to do all of these, but you may pick and choose based on your situation: