A Sewer Smell Is in My Basement After I Flushed the Toilet Upstairs

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Drain traps are elbow pipes that hold water to seal off sewer gas.

A sewer smell in your basement, after you have flushed an upstairs toilet, indicates an issue with the drain system. Sewer smells are typically present when sewer gas escapes from the sewer and makes its way into your home or basement through the drains or a leak. There are a few potential causes to consider before calling the plumber.


Cracked Drain

A cracked drainpipe can cause a sewer smell when the toilet is flushed. If the crack is located along the top of the drain, most of the time sewer gas, and not water, would leak out. As the water from the toilet is dumped into the drain, the increase in pressure forces gas out of the pipe, causing an odor in the basement. Examine the drainpipe closely for any signs of cracks, splits or holes.


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Clogged Drain Vent

All household drains need to be vented in order to continue flowing freely. When water flows down a drain toward the sewer, it creates an area of higher pressure in front of it and lower pressure behind it. If there is not proper ventilation, this pressure differential can lead to backups and slow draining, which can cause an odor to permeate throughout your home. Examine the drain vent for signs of clogs. The drain vent is typically located on the roof and is a metal pipe that stands a foot or two off of the roof. An ordinary garden hose can be snaked down the vent and turned on to push out any clogs or debris.


Washing Machine Standpipe

Many homeowners opt to put their washing machine in the basement. Washing machine drains are a bit different from other drains. The drain hose from a washing machine is tied in to a standpipe, which is a wide, standing metal pipe. The standpipe acts as a sort of buffer for the drain, holding the large amounts of water the washing machine drains after the rinse or soak cycle. If this standpipe is improperly installed, it is open to the air and can easily leak sewer gas. Ensure your washing machine standpipe is installed properly and is up to code.


Drain Traps

Drain traps are a requirement for every household drain. These are small, elbow-shaped pieces of pipe that remain filled with water. This prevents sewer gas from backing up from the sewer or drain line and leaking into the home. If you have a drain without a drain trap, it is a good bet that sewer smell is emanating from that drain. Install a drain trap, as soon as possible, since sewer gas can be harmful to your health and may pose a fire risk.



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