Why Do My Drains Smell Bad in the Winter?

If your kitchen, bathroom or laundry room drains are particularly stinky during the winter months, you're not alone. Trapped grease, dried-up P-traps and frozen pipes can all make drains smell bad in winter, and they may be more noticeable when your house is closed up to keep the heat in.

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While nobody likes a smelly drain, the good news is that you can usually remedy the issue yourself or with the help of a professional plumber.

What Are Some Reasons My Kitchen and Bathroom Drains Smell Bad in Winter?

A variety of plumbing issues can cause drains to smell bad in winter. Here are some common causes of drain odors due to winter-specific plumbing mishaps:

Frozen Sewer Pipes

When outside temperatures dip below freezing, water and waste in underground sewer lines can freeze. If portions of the sewer line freeze, it may prevent proper drainage and trigger odors in your pipes.

Blocked Exterior Vent Pipes

Most home plumbing systems are designed with vent pipes that vent odors and gases outside. If the exterior vent opening freezes up, this can lead to trapped odors that may work their way out through your drains.

Trapped Grease

If you have trapped grease in your kitchen drain pipes, cold winter temperatures can cause it to freeze and solidify. As the grease melts over time, you may notice a foul smell caused by bacteria and organic matter.

Dried-out P-traps

A P-trap is a U-shaped plumbing pipe commonly found under kitchen and bathroom sinks. The U-shape allows the pipe to hold a small amount of water, which prevents sewer gases from moving up the pipes and out of the drains. In some cases, dry winter air can cause the water in the P-trap to evaporate. The lack of water makes it easier for sewer gas to travel through the pipes and cause a sewage smell from the drain.

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How to Fix Stinky Drains This Winter

If your drains smell bad due to trapped grease or a dried-out P-trap, you may be able to solve these issues yourself. However, it's important to contact a plumber right away if you smell sewer gas, as prolonged exposure can be dangerous. Here are some tips on fixing bad-smelling winter drains based on the root cause:

Trapped Grease

To dissolve frozen grease in your pipes, mix a pot of near-boiling water with several squirts of dish soap. Pour the soapy mixture down the drain. The hot water should help dissolve the solidified grease and eliminate the odor. If your drains still smell after trying this DIY method, contact a plumber.

Blocked or Frozen Exterior Plumbing Vent

If the bad drain smell is due to a blocked or frozen exterior vent, hot water may help melt the ice from the inside out. Start by turning on the faucet that connects to the exterior vent to relieve any internal pressure, and run the water on hot. The warm vapors from the hot water may help melt stuck ice. If this remedy doesn't work, the next step is to call a plumber who can safely access the vent via your roof.

Dried-out P-trap

Some common signs that can indicate a dried-out P-trap include gurgling sounds coming from your pipes and odors emitting from the drains. In some cases, pouring a gallon or so of water into the affected drain is enough to remedy the issue. However, if your drain is giving off a strong sewer gas smell, it's best to consult a professional plumber to ensure safe and efficient repairs.

Frozen Sewer Pipes

In addition to drain odors, signs of a frozen sewer pipe can include gurgling sounds coming from your pipes, reduced or zero water flow and slow-draining water. Under pressure, frozen pipes can sometimes burst and cause flooding and water damage. If you suspect a frozen pipe is causing the odors coming from your drain, it's important to call in a licensed plumber. They can use specialized tools to thaw your pipes and add wrapping or insulation to help prevent future issues.