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Closing up the cabin for the winter

Media Contact: Allison Sandve, U of M Extension, (612) 626-4077,

ST. PAUL, Minn. (10/9/2013) —For seasonal homeowners closing a septic system for the winter helps prevent the system from freezing, prolongs the life of the system, and keeps it operating at a high level. Doug Malchow, University of Minnesota Extension Water Resource Management Educator, has some tips to consider when preparing your cabin's septic system for the winter months.

Preparing the Drainfield

  • Stop cutting the grass over the drainfield in mid-September; the extra grass length will capture snow, which provides insulation. Consider placing snow fence near the drainfield to help capture drifting snow on the drainfield to add to the natural insulating blanket of snow.
  • Make sure all inspection pipes have covers to keep cold air from flowing into the drainfield pipes.

Winterizing the Water Pipes in the Cabin

  • Do not add automotive antifreeze, salts, or any other additives to your plumbing.
  • Even if the heat is left on, it is still a good idea to drain water supply lines. Shut off the water where it enters the house and drain all lines.
  • Drain the pump and then run it for a couple of seconds to be sure all water is out of the lines. Drain the system by opening all the faucets, and then leave the faucets open.
  • Completely drain the pressure tank. Flush the toilets and add RV antifreeze to the toilet tanks at the recommended dilution ratio.
  • Check flexible hoses in sinks and bathtubs to be sure they are drained completely. Remove and drain inlet hoses for the dishwasher and clothes washer. Clear the water valve by starting the machine for a few seconds; then drain the tub. Remove the drain hoses and drain completely. Disconnect the electrical supply to the pump, water heater, softener, washer, and dishwasher.
  • Drain the water heater and water softener with a hose after power is disconnected. RV antifreeze can be added to traps in sinks, bathtub and shower drains, washtubs, floor drains, and sump pumps.
  • If you do not drain the water lines for the winter, be very sure that there are no leaks or drips. This constant, low flow of water can cause septic system freezing.


  • If you have a high efficiency furnace that is left on for the winter, be sure that there is no water drip from the furnace that enters the septic system. This small trickling of water into the septic system can cause the system to freeze.
  • Re-route the drip water to a floor drain that does not enter the septic system or reroute to another water source that enters the septic system in larger amounts.
  • If shutting off the furnace, drain all water from forced hot water and steam systems unless the system contains antifreeze; call a plumber for assistance.

Cleaning/Pumping the Septic Tank

  • Consider pumping the tank if closing the cabin for the winter. If a tank is left full but the system is not used during the winter, the sewage will get very cold or possibly freeze. If you live in an area with a high groundwater table, you should only pump the tank if it was designed for such conditions.
  • In the spring, it will take some time for the frozen sewage in the tank to thaw, meaning the septic tank may not be able to accept fresh sewage until the sewage in the tank thaws.

Adapted from a paper posted on the Onsite Sewage Treatment Program webpage.

For more information about this topic or other septic topics, visit

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