A Septic tank does can sometimes smell a little bit. However, the odour should not be noticeable in a well-installed septic tank.
In this article, we’ll look at some of the common causes of that "septic tank pong". Here are 7 possible contributing factors that can lead to the development of odour:
We break food down in our bodies, removing a lot of nutrients and leaving only waste. This waste enters the septic tank and settles to the bottom, bacteria in the septic tank will break down a portion of it and the rest has to be removed once a year. If you add food (by using a food disposal unit) you are adding waste that hasn’t already undergone a process of being broken down (in our bodies). There isn’t the right type of bacteria in a septic tank to fully break down food and therefore it rots. When this happens, it will smell of rotting eggs. If you have a pungent smell from your septic tank the first thing to do is avoid any food entering the tank.
You may enjoy fresh sheets every day, and a perfectly clean house. However, you may be harming the bacteria in your septic system. Detergents and chemicals can harm the bacteria within the tank. Limiting the use of strong bleach and cutting down on detergent will help to prevent smell in your tank.
Most houses are fitted with a soil stack, which allows fumes from a sewer to go up through the vent and out above the roof.
when a house has a private septic system, it is important to make sure this air flow is correct. Air must flow out of the soil vent pipe. For air to flow out, air must flow in. A good analogy here is imagine leaving the front door open in your house, if no other windows or doors are open then nothing happens. If you however open the back door, you let airflow through the house and a door might bang shut.
This is similar to what needs to happen with your septic tank ventilation, you need to have a way for fresh air to come into the septic tank to enable the poor quality air to flow up and out of the soil stack. The addition of a sewage wind ventilator (or otherwise known as "Rotary Cowls") will pull air up through the soil stack.
If you don’t have a low level vent on your septic tank to let air in, try introducing one (speak to your builder or a specialist if you are unsure). Also consider adding a maxi vent which has carbon in to remove some of the odour. If you are doing this it is important to establish where the odour is coming from. There is no point putting a maxi vent on a soil stack if the smell is coming from a manhole cover
Top tip: Employing an sewage specialist to test the ventilation will soon tell you if you have a problem. Sewage specialists use smoke to visually show the direction of air travel.
A regular soil stack allows air to freely flow up the soil stack and out of the property over the roof of the house. Air admittance valves are sometimes installed by plumbers or specified by architects when designing the building. These valves prevent good air flow and whilst are fine on mains sewage. However. they are not to be used if you have an off mains solution like a septic tank or sewage treatment plant. If it is not possible to remove the valve and replace for a normal one, then you could attempt to add a high level vent up the side of the property or up a tree before the septic tank, to draw gas up and out.
Each year a septic tank should be de-sludged, this process removes the build up of solids in the tank. You may have heard people say “it’s been in 50 years and only emptied once”. This persons septic tank may not smell because their ventilation is good, but their drainage field may be really blocked up! So please keep on top of emptying the septic tank.
A U-bend prevents gasses coming up through the toilet. The water within it acts as a barrier for to prevent smell getting through. If this dries up then odour will be released causing smells in the bathroom. To prevent this from happening, make sure a loo is flushed every month.
If you are experiencing smells in the house and you have ruled out point 5, then it is possible that air could be getting in via a crack in the soil stack running up through the walls. If it is a new build then contact the builder to discuss this.
If your system is smelling, then firstly look to what you are putting in it and how frequently it is being emptied. Read our guide on what not to put in your septic tank. If you are very satisfied that you are using it correctly then you should look to the ventilation and ensure there is good airflow up through the soil stack and out of the roof.
If it is smelling then you could also consider converting it into a sewage treatment plant to better break down the waste.