Septic tanks are concealed underground structures built to treat waste water from household plumbing. This water is produced from bathrooms, toilet, kitchen drains and laundry.
When full, septic tanks emit stinking gases that are not only disgusting and unbearable, but also harmful to human life as they can cause diseases.
Baker Mwesigwa, a plumber from Kyambogo, Kampala, says mysterious pools of water around the septic tank, leaky pipes, and malfunction of toilet flushing systems are among the signs of a clogged septic tank that needs to be emptied.
Mwesigwa advises that you open the lid of the tank and observe the levels of sludge to find out whether it requires emptying.
Besides a full septic tank, there are other factors that can cause this bad smell and homeowners ought to get rid of it as soon as possible.
Mwesigwa advises that both inside and outside plumbing should be properly done to ensure a good and long lasting septic tank.
“Make sure the interior pipes are well connected and the covering of the outside pit floor of the septic tank well done with enough cement to cover all the edges where gases can pass to pollute the environment,” he says.
Mwesigwa further advises that the manhole cover should be tightly secured to avoid bad odour from escaping. Septic tank manholes should be covered by a reasonable amount of soil, at least 13 inches.
Sharing her experience, Benitah Nakagiri, a landlady, says, it was hardly five months when tenants entered her new apartments when the septic tank started stinking, causing a lot of discomfort in the neighbourhood. She was advised to properly cement the outside covering of her tank, which she did and the rest was history.
Drains should have water
Drain fields are made up of parallel pipes that take care of emptying the waste water. They allow liquid waste to be filtered into the ground.
Emmanuel Ondoa, a plumber at Kai Constructions, says drains of a septic tank have a U-shaped bend in the pipe designed to hold water and keep gasses from rising up where you do not want them.
Ondoa adds that if the water in these gutters dries up, the odours begin to travel up the pipe into your home. He, therefore, advises that in case this happens, home owners should start running water into the drains, especially in areas that are rarely used, for example, the guest bathrooms or even when you have taken days without using the bathrooms, toilets and the sink.
Unblock the vent stack
The vent stack is the pipe that releases all the gases that build up in your septic tank.
It sends these gases out over the roof such that the smell does not affect people. However, when leaves and other foreign bodies get blocked inside, they cause odour to be trapped around your house.
To prevent this, Mwesigwa advises home owners to always clean the roof and gutters of their houses so that leaves do not block the stack.
“To reinstate proper functioning, you should carefully remove foreign bodies from the vent stack,” he says.
Check faulty rings and seals
A wrongly sealed or broken connection around one of your pipes can also emit smells from the septic tank. This commonly happens near the base of the toilet.
Ondoa says it normally emits a strong sewage stench, especially in the bathroom. He adds that it is very common in older homes where seals can loosen or get damaged over the years.
Seek professional help
For this problem, he advises home owners to seek the help of a qualified plumber because if they attempt to fix it themselves, they may cause more damages.
IS SEWER GAS HARMFUL?
When the organic household wastes from the household decompose, a smelly gas known as hydrogen sulphide is released. It is this gas that smells like rotten eggs or beans, which most people refer to as sewer gas.
Dr Francis Mubiru of Nalinya Medical Centre in Kangulumira, in Kayunga District, says hydrogen sulphide gas that is emitted by sewage tanks can be harmful depending on the levels emitted as well as the person smelling it.
The gas can cause stomach disorders, fatigue, and loss of food appetite, vomiting and dizziness. However, he says these upsets can cease when one gets away from this gas.
“The sewage, smell has no much effect on one’s body, but the hydrogen sulphide gas and other gases emitted from sewage tanks can cause body upsets,” he says.
How sewer septic systems work
A septic tank is simply a big concrete or steel tank that is buried in the yard. The tank might hold 1,000 gallons (4,000 liters) of water. Wastewater flows into the tank at one end and leaves the tank at the other.
There are three layers. Anything that floats rises to the top and forms a layer known as the scum layer. Anything heavier than water sinks to form the sludge layer.
In the middle is a fairly clear water layer. This body of water contains bacteria and chemicals like nitrogen and phosphorous that act as fertilisers, but it is largely free of solids.
Wastewater comes into the septic tank from the sewer pipes in the house.
A septic tank naturally produces gases (caused by bacteria breaking down the organic material in the wastewater), and these gases don’t smell good. Sinks therefore have loops of pipe called P-traps that hold water in the lower loop and block the gases from flowing back into the house. The gases flow up a vent pipe instead if you look at the roof of any house, you will see one or more vent pipes poking through.
As new water enters the tank, it displaces the water that’s already there. This water flows out of the septic tank and into a drain field. A drain field is made of perforated pipes buried in trenches filled with gravel. The following diagram shows an overhead view of a house, septic tank, distribution box and drain field:
A typical drain field pipe is four inches (10 centimeters) in diameter and is buried in a trench that is 4 to 6 feet (about 1.5 m) deep and 2 feet (0.6 m) wide. The gravel fills the bottom 2 to 3 feet of the trench and dirt covers the gravel, like this:
The water is slowly absorbed and filtered by the ground in the drain field. The size of the drain field is determined by how well the ground absorbs water. In places where the ground is hard clay that absorbs water very slowly, the drain field has to be much bigger.
A septic system is normally powered by nothing but gravity. Water flows down from the house to the tank, and down from the tank to the drain field. It is a completely passive system.
You may have heard the expression, “The grass is always greener over the septic tank.” Actually, it’s the drain field, and the grass really is greener -- it takes advantage of the moisture and nutrients in the drain field.