Why does my house smell like sewage?

Frequently Asked Questions

The smell of sewage indicates something wrong somewhere in the plumbing system. Follow the smell to see if it’s coming from a fixture or particular area and if you are having troubles locating the source you can give Plumbtech Plumbing a call to isolate the source, diagnose the cause, and fix it. The Barrie-based company receives numerous calls about sewage smells daily.

The Hazards of Sewage Gas

Beyond the obnoxious smell, it’s best to eliminate the odour sooner than later because it could be hazardous to your health. Sewage creates bacteria and a mix of gases that range from hydrogen sulfide, methane, ammonia, and carbon dioxide. The actual smell of sewage comes from hydrogen sulfide. Physical symptoms can range from fatigue, headaches, nausea or vomiting, dizziness or lightheadedness, and poor memory and concentration depending on how high the level is.

Fire Hazard

Methane gas is dangerous. Some, in their search for the sewage smell, have lit the flame on a lighter in an attempt to look into the drain. That is not a good idea because the gas emanating from the drain can catch on fire and create an explosion. It would be better to use a flashlight or call Plumbtech to investigate. The plumbers can run a snake through the drain or send a camera into it to see if there is a blockage as well as its location within the pipe.

Drains & Sewage Smells

Drains can be one of the common causes of a sewage smell. It is more likely to be the result of water that has dried up in the drain than a bad odour from a blockage in the pipe. When the water dries up in a drain or a trap from lack of use, sewer gas will rise in its place. This can occur in a floor drain in the basement, a shower, or a sink that is used infrequently. The floor drain is usually located on the lowest part of the basement floor. It connects to a drain line underneath the floor that goes to the main drain pipe and municipal sewer system or septic tank.

The floor drain is designed to remove water that has come into the basement because of heavy rain, a major snow melt, a leak from a water heater, and more. If that does not happen or if it only occurs infrequently, the water in the floor drain can dry up. Prevent that from happening by
pouring some water down the floor drain from time to time.

In a sink or shower, there is a U-shaped trap that holds a portion of the drain water to prevent the rise of sewer gas. To prevent it from drying out, turn on a tap, and let water flow down the drain from time to time. Adding a little bit of vegetable oil to the drain will help prevent the water from drying in a fixture that doesn’t get used a lot.pouring some water down the floor drain from time to time.

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Common Causes of a Sewage Smell in your House

There are a variety of other situations where the smell of sewage can occur. Everything in the plumbing system is connected, from the water coming into the house through waterlines to the sinks, shower, and toilets. The outgoing water and wastewater run down the drain of each fixture to hook up to the main drain line, which flows into the municipal sewer system or septic tank. The smell of sewage could be coming from a loose or old, dried-out toilet seal, a clogged sewer vent pipe, or something more serious such as your main drain/sewer line.


There are two different reasons the smell of sewage comes from a toilet. The most common reason is a seal has dried up or cracked, the floor underneath the toilet has deteriorated, or the toilet is loose. This seal also called a toilet gasket or wax ring seals the toilet bowl to the floor. This prevents water and sewage from leaking out onto the bathroom floor. If there has been a renovation and the floor level has changed from linoleum to tile, for example, an adjustment will need to be made when replacing the toilet. It will affect the seal between the toilet bowl and the floor.

There could also be an issue with the toilet flange, which bolts the toilet to the floor. It looks like a disc with holes. The flange can break if stressed by a change in floor level or if the toilet is loose. The flange connects to the toilet base which leads to the main drain sewage pipe or septic. To bridge the thickness gap, a renovation flange can be added to make up for the height difference. Alternatively, a double or thicker gasket can be added to raise the toilet to the new floor level.

Residents of a multi-story building can be impacted by another issue that affects the toilet seal. As heat rises through each floor, the wax ring softens and deteriorates. A foam-type gasket is recommended in these applications.

Clogged sewer vent pipe

A vent pipe is an essential part of all plumbing systems. It helps to regulate air and releases sewer gas from fixtures such as toilets, sinks, and showers. As the vent pipe rises through the roof, heavy snowfall can plug it if the vent isn’t high enough. If there is a higher building or hill nearby, the building located on the lower level may get a downtown draft from the higher one. The downdraft means the wind is going into the vent, so the sewer gas cannot vent naturally. Plumbtech can install a 180-degree elbow in the vent pipe, which will help to correct the problem in some applications.

Sewage Pit

A sewage pit can be found in a basement or at a cottage. The pump inside the pit may need to have the rubber grommets replaced, and/or the pump may need to be resealed. The access panel may also need to be resealed.

Septic Tanks

Septic tanks are part of a septic system. To make sure everything runs smoothly, the tank(s) will need to be pumped out regularly. How often depends upon how much it is used. If it isn’t pumped out, it will back up and smell bad.


All homes are required to have a cleanout as a part of the plumbing code. It is usually found at the front of the house, inside on the floor. Cleanouts should also be located on a drain pipe under a kitchen sink and laundry tub. It is capped and sealed to make sure sewer gas does not escape. Because they don’t have a trap, all cleanouts have a seal, a rubber ring, or a Teflon seal or gasket which may need to be replaced if there is a sewage smell.

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