The septic venting pipe and system provides a septic tank the ability to move gases and air out of the tank when it fills up with waste and liquid volume. This basic release system is essential as a blockage stops the tank from working. This in turn causes the septic system to back up right to the toilets – not a pleasant situation to fix.
Septic tanks involve essentially a large steel or concrete container buried underground outside a home or structure. The typical volume on such a container tends to be approximately 1,000 gallons. The tank itself is connected to the pipes and toilets inside the adjacent structure. When the waste system is used, the waste is washed through the pipes, out of the structure and eventually into the tank. The waste settles to the bottom to decompose while the water flows on to the municipal system or a leech/drain field.
The Role of the Vent
When a tank is empty, it is a giant cavity. This is essentially made up of air. However, because the tank and its plumbing system are closed, that air gets trapped. As the septic tank fills with waste and water, the air has to go somewhere or the pressure will stop the flow and back up into the structure. To solve this problem a vent is connected to the top of the tank to release the waste gases and air outside.
Speed of Venting
Because septic tanks operate with nothing more than gravity, the amount of air that gets vented depends on how fast the tank fills up or dries out over time. As long as the air can push through some exit, the flow into the tank will continue properly absent any other blockage.
Unfortunately, as septic tanks vent, the smell from the contents comes out with the venting. Depending on which way the wind is blowing, movement in the tank can create an odor that can blow back toward the structure. For those with septic tanks, it seems to be a lesser evil to deal with as long as the tank continues to work. However, by increasing the height of the vent pipe out of ground, the odors can be released at a higher level, possibly blowing over the structure in the wind.