Sewer Gas Problems in Very Cold Weather

Air Pressure Changes

• When the temperature outside falls and the temperature inside rises, as it does during the winter when the heat is on, natural convection occurs. This is usually only a problem in multistory commercial buildings. The warm air rises to the top of the building, creating a negative pressure zone in the lower floors. This can slowly draw up sewer gases from any drains that are not plumbed properly, and may make a sewer gas problem that is not noticeable during the warmer seasons suddenly intolerable. The presence of sewer gas inside your home always necessitates repair, regardless of the season.

Septic Issues

• If you are presented with sewer gas problems in very cold weather and have a septic tank, you may in fact be dealing with a frozen septic field. The septic field is the area around the septic tank into which the tank disperses waste water. A frozen septic field will prevent the septic tank from properly draining and can cause backups. The septic field lines will need to be repositioned beneath the frost line to prevent freezing.

Dry Traps

• Traps use water to keep sewer gas in your drain line and out of your house. A trap is a U- or elbow-shaped piece of pipe. The bottom of the elbow holds water and forms a seal against any gas emanating from the sewer line. Over time, the trap in a drain that is not frequently used can run dry. This can especially be a problem during the winter, when humidity levels are low and you have been running your heater at full blast. Luckily, simply running some water down the drain for a few minutes will refill the trap and, if it is in good working order, seal off the sewer gas and prevent it from leaking into your home. If dry traps are a recurring problem, install a trap primer, which will periodically add water to your traps.

Frozen Vent Pipes

• Vent pipes run from your drain lines to your roof. These pipes allow air into the line, which prevents the water exiting your house from creating a vacuum and helps water drain more easily. Rooftop vent pipes can become clogged by leaves, bird nests and even dead animals any time of year, but during very cold weather, steam flowing up the vent pipes from shower or laundry drains can condense inside the pipes and freeze. Heavy snowfall also can accumulate on your roof and cover or clog the vent. This can restrict or stop the flow of air and interfere with proper draining, which can result in sewer gas backups.