The bacteria active in a septic tank are anaerobic. Anaerobic means the bacteria operate without oxygen from the air. The result of their anaerobic activity generates odours, the most common of which is hydrogen sulfide gas. The odour from hydrogen sulfide is like the odour of rotten eggs…not too pleasant!

There is not a great deal of gas generated in a septic tank, but the gas must be released so pressure does not build up in the tank. Odours are also more prevalent before a crust forms on the water in the septic tank or bacteria in the tank is unhealthy. It is important be mindful of what you put down your toilet and sink etc. Downdrafts along the side of the roof where the vent is located may be caused by wind blowing over the roof from the opposite side. Wind blowing over nearby trees, which are higher than the house, can also cause downdrafts. The downdrafts may occur only when the wind is from a certain direction and at a certain speed. This is why the odours may happen only every now and then. If the top of the vent pipe is not far enough above the roof line, wind currents may carry the odours along and down toward the ground.

What are the solutions to the odour problem?

One simple solution may be to lengthen the plumbing vent and extend it well above the roof line.Septic venting