One in four American households has an individual septic system. Many live in cold climates where the ground freezes. Care must be taken fall, winter and spring to maintain a septic system through the winter and prevent freezing issues.
On-site septic systems are effective methods to treat and clean wastewater, returning clean water to the groundwater system. This groundwater is the source of drinking water for millions of people; we all want it to be clean and safe.
Homeowners need to provide maintenance on a regular basis for septic systems. It is critical that the system be inspected and prepared for winter in cold climates.
Why Septic Systems Freeze
Individual septic systems may freeze due to several possible causes, or a combination of causes. Some of the common causes include:
- Lack of snow cover: This is one of the most common causes of frozen septic systems. Snow acts as an insulator, protecting the septic system drainfield or mound. There are air spaces between the snow flakes, which traps warmer air. This forms an insulating blanket over the soil.
- Compacted snow: With the air spaces removed, compacted snow cannot act as an insulator.
- Cracked or missing inspection pipe covers: This allows cold air, rain and snow to enter the system.
- Compacted soils: Compacted soils can cause several problems. Soils that have been compacted by traffic such as cars or even bicycles no longer have air spaces, which act as an insulator. In addition, compacting soils can cause pipes to shift, losing the gravity flow or even breaking pipes apart.
- High-efficiency furnaces: When a furnace cycles, a small amount of water condensation is released. If this is directed into the septic system, the small amount with no pressure can stop in pipes with inadequate gravity flow and freeze there.
- Lack of adequate or appropriate plant cover: Grasses and other landscape plants act as an insulator and trap snow. If the system is new so plants have not yet established, the drainfield area must be mulched.
- Leaky pipes, faucets, toilets: Water constantly dripping into the system can cause system over-load and freezing.
- Irregular use of system: This is a common cause of freezing at cabin properties, or if the homeowners are “snow-birds.” Regular inputs of warm water do much to prevent freezing.
Steps to Prevent Freezing
These are some of the ways to prevent a septic system from freezing:
- Put 8 to 12" of mulch over the drainfield, tank and pipes. Do not forget the pipes from the house to the tank. Use straw, old hay, leaves or an insulating blanket. Remove the cover early in the spring to encourage grass growth. In northern climates where the ground freezes deep, watch the weather forecasts. If a cold spell arrives by Thanksgiving without snow cover, mulch the system. The mulch must be in place before sub-zero temperatures arrive to be effective.
- Keep all traffic: cars, snowmobiles, 4-wheelers, dirt bikes, bicycles off the system all year. These vehicles cause compaction of both soil and snow.
- Check for cracked and missing inspection pipe covers spring and fall. Walk around the drainfield and tank, checking all the inspection pipe covers. Make sure they are present, and in one piece. New covers are readily available at hardware stores.
- Consider re-routing furnace drip water from the system. Send it to the sump pump drain, collect in a bucket, or drain directly outside of the house. This is a clean-water source, meaning it does not need to go through the septic system.
- Establish good plant cover with landscaping techniques. There are a number of options in addition to turf grass to make the system fit into the home landscape.
- Routinely check toilets, faucets and other water sources for leaks, repairing as needed.
- Seasonal cabins often have freezing problems, as do systems where the property owners are absent part of the winter. The easiest solution is to have someone run warm water at least weekly. For example, invite the neighbors to do their laundry at the home while gone.
- It may be best to close cabins up for the winter, draining water sources. This factsheet provides full directions. Check with local septic pumpers regarding if the tank should be pumped for the winter. This advice varies due to types of soil, type of tank and other factors.
Protect Septic System, Prevent Freezing
Every season change, do a walk around the yard and system. Check for low spots, excessive or minimal grass growth over the system (may indicate over or under use), inspection pipe caps, and anything else visible.
Be sure to have the tank pumped regularly, at least every 3 years. Check with local officials regarding local rules and regulations.
Resources for More Information
Septic System Maintenance for Individual Systems
Landscaping Septic System Drainfields and Mounds
Septic Systems: Care of Inspection Pipes, Locating Septic System
Freezing Problems & Septic Systems, University of Minnesota Onsite Sewage Treatment Program.
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Valerie Prax - Valerie Prax recently retired after nearly 35 years with University of Minnesota Extension. She served as an Educator and Professor for 27 ...
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