What causes septic tank odour?

Every now and then, homeowners complain about odours coming from their septic tank. When this occurs, the odour can be unbearable and can cause a great deal of embarrassment.

When there is an odour coming from the septic tank, the cause should be quickly investigated.

What causes septic tank odour?

Why do septic tank odours occur?

Odours from a septic tank tend to occur because the organic gases that are supposed to be neutralized or escape into the environment somehow get redirected back into the home.

Common gases that can create a foul odour include methane, hydrogen sulfide and carbon dioxide. Besides the smell, these gases can be toxic, irritating and sometimes cause explosions. The main causes of septic tank odour include the following:

Dry drains

Dry drains are one of the most common causes of septic tank odour. Septic tanks have a built-in trap device in the pipe. The function of this U-shaped pipe, which contains water, is to make sure that gases do not seep through. However, if the U-shaped tube is dry or dirty, the odour immediately enters the home. This is a common problem in the bathroom. The solution is to add water to the drain or clean any debris from the U-shaped tube.

Cold weather and more

Cold weather is another common reason for strong odour in the home. During frigid weather, frost often develops around the plumbing vent, causing it to block and become non-functional. When such a block occurs, the sewer gases will be redirected back into the home and outside as well. During the winter, it is important to check the plumbing vent and keep it from freezing.

Another reason for septic tank odour may be a poorly sealed cover on the ejector sump pump basket. The covering should be evaluated and if a leak is present, a new seal can be installed.

Surface runoff

Surface runoff is a problem that can occur during periods of heavy rainfall. The surface or ground water runs into the tank, causing it to overflow. To resolve this problem, insert an intercept drain to prevent the ground water from running into the septic tank.

Home renovations, strong winds and waste

Sometimes when homes get renovated, the old septic tank may get covered or blocked. If the room that was previously used to vent the gases has been altered into something else, that room will start to stink.

All septic tanks have a vent installed. The function of this vent is to permit noxious gas to escape from the sewage and prevent toxic and flammable gases from building up in the tank. Anything that causes this vent to block or clog, such as animal waste, leaves, frost or ice, can cause this problem.

Strong winds can redirect septic tank gases back into the home. In such scenarios, the vent stacks have to be unclogged and the height raised. Carbon filters can be installed on top of the vent to absorb the noxious gases.

The final reason for septic tank odour is a tank full of waste, which leads to clogging. To solve this problem, ensure that the septic tank is regularly pumped or emptied.

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