Plan for the septic tank

Two months ago, Petit Najjemba woke up to a foul smell in her house. At first, she thought it was the garbage truck that normally passes by every Saturday morning. But after 30 minutes, the smell had not yet gone away.

“I asked one of the house helps to go out and look for the source of the smell. After moving around the compound, she found that the septic tank had filled and its contents spilled into the compound.”

WHAT IS A SEPTIC TANK
A septic tank is one of the important facilities in a home although it is given less attention during planning. Moses Mutelya, a senior plumber working with Togo Construction Company, describes it as a big concrete, steel or plastic tank that is built underground to collect waste generated in a home from sinks, bathrooms and toilets. They are buried in the yard of your home. Waste water enters the tank at one end and leaves the tank at the other end.
Septic tanks are meant to treat waste. They are used in places where there is no main connection to a public sewer provided by the local government or private corporations.

TYPES
Plastic tanks
These are the cheapest of all the tanks and if you are working on a tight budget, you can use these,” Moses Mutelya, a senior plumber working with Togo Construction Company explains adding,
“They are good for waterlogged areas but also need a strong flat bottom. If the bottom is not strong, then the water will go through and push it up and out of the ground.”
He adds that before it is placed under, the engineer must fill it with water so that it doesn’t deflate.
“This particular type must be installed by a professional plumber or else it will collapse,” explains George Akankwasa, another plumber.

Advantages
Mutelya says plastic septic tanks are advantageous if a home owner has limited space because they require little space and work well in areas that are swampy.
Another advantage of using plastic septic tanks is that if a home owner wants to change the location of where the tank is placed, they can because it is not a permanent structure.
Mutelya says this type also covers up properly because it has one hole. He says the disadvantage of having plastic septic tanks lies in the capacity of sewage that they can contain because if it is large, it will collapse.
These have to be checked every three to five years, depending on the size that you used. Those that are constructed for three to five users (people living in the house) can be checked after five or seven years depending on how it is being used.
The other one is set for five to seven users and has to be emptied in a period of three to five years.

Concrete/brick tank
This is the traditional type of septic tank used in Uganda. It is the most expensive to construct and it can be constructed in both dry and swampy areas.
Mutelya says this can be constructed with iron bars, sand, cement, stones and bricks; it can be plastered for a neat finishing.
Concrete septic tanks are easy to maintain and can be constructed to hold between 20,000 litres, and 60,000 litres.

Advantages
Mutelya adds that the advantage this type of tank is that it takes 15 to 30 years to fill up.
He says a soak pit is a major requirement for this type of septic tanks and it is important to use air tight covers so that the smell from the sewage does not escape.
Use of proper ventilation in your toilet will also help release bad gases into the air and reduce on the burden on the septic tank.

CONSIDERATIONS
Moses Mutelya, a senior plumber working with Togo Construction Company, explains that it is important to consult with a professional plumber before constructing a septic tank. This is because it is important to know the type of soil that is suitable for the septic tank that one has in mind.
“You should know whether the area you leave in is swampy or rocky so that you can get the suitable septic tank for your home,” he adds. He says that it is also important to discuss with the client to know what their preference is in regard to where to place the tank and the type they would prefer for the home. A plumber should not dictate the details of the construction of the septic tank.

WARNING SIGNS
Moses Mutelya, a senior plumber working with Togo construction company, says the warning signs that yours septic tank is overloaded are: sluggish toilet flushing, plumbing system backups, gurgling sounds in the plumbing, ground is boggy or wet over soil treatment area, odours inside or outside (tank/drains not vented or tank not emptied regularly), low spots in the area over soil treatment system, the septic tank rapidly fills up after emptying (water running back from effluent disposal system)

COSTS
George Akankwasa, a plumber, says the cost of making a plastic septic tank depends on the size that you want. A tank that can hold 100 litres will cost up to Shs600,000, for 160 litres will cost you about Shs1m and the largest one which can hold up to 5,000 litres will cost about Shs4m but he advises that this size is not recommended. The construction of a concrete or brick septic tank will cost you more than the plastic tank because in the construction of the concrete septic tank, a lot of material is required. These include stones, concrete, iron bars, bricks, sand, cement and labor inclusive. All this will cost a client up to Shs3.5m, labour inclusive.

MAINTENANCE
Frank Tumushabe, a plumber says the most important things to remember about your septic system are:
1. Do not overload it. Exceeding the capacity of the septic tank system can cause surface discharges. These discharges can create a health hazard on your property and pollute nearby water sources. Depending on the design of your septic tank system, you may be able to expand its capacity if necessary.
2.He says it is important to measure sludge and scum depths or routinely pump out the septic tank at least once every year if you own a plastic septic tank mostly. But all septic tanks need pumping to reduce sludge and scum build-up. If you do not pump out your tank periodically, solids may wash out of the tank into the soil treatment system, thus limiting its effectiveness.
3.It is also important not to put strong or hazardous chemicals into the system. Septic tank systems are designed to treat normal, household domestic sewage. Substances such as paints, paint thinners, solvents, pesticides and flammable liquids can kill the bacteria that provide the treatment in the septic tank and the drain field. Furthermore, these chemicals can flow through the soil and contaminate surrounding ground water, making it unsafe to drink.
4.Keep grease out of the system. It can easily block up the works and inhibit the bacteria that are necessary for proper functioning of the septic tank system.
5.Toilet paper is fine, but don’t put other paper products such as cigarette butts, sanitary napkins, paper towels and disposable incontinence pads or nappies (diapers) into the system.
6.Laundry waste water contains soaps, dirt and grease, and should go into the septic tank not directly into any soil treatment system.
George Akankwasa, a plumber, says if cared for properly throughout the years, you can make your septic system last for a very long time.
He says there are different sewage companies that can pump out the scum.
“However, if you do not know of any, you can consult with your plumber, they will always recommend some one.

DISTANCE FROM THE HOUSE
“The recommended distance of the septic tank from the house is 30 metres but that is almost equivalent to a plot of land in Kampala,” Moses Mutelya, a senior plumber working with Togo Construction Company says.
He says, you can put it at a distance of 10 metres from the house and if you have a garden in you home, it is better to put it there. For a concrete tank that does not require to be changed quite often, you can place it in the compound and allow the grass to grow over it.

HOW THE SEPTIC system WORKS
Dealing with the smell. Septic tank naturally produces gases (caused by bacteria breaking down the organic material in the waste water), and these gases produce a foul smell. 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.

Separation. 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 National Water and Sewerage Corporation drain field. A drain field is made of perforated pipes buried in trenches filled with gravel. Untreated waste water from the house flows into the septic tank, where the solids separate from the liquids. Some solids, such as soap, scum or fat, will float to the top of the tank to form a scum layer. Heavier solids, such as human and kitchen waste, settle to the bottom of the tank as sludge.

The drainage process. The remaining liquids flow out of the tank to a land drainage system or drain field. Baffles built into the tank hold back the floating scum from moving past the outlet of the tank.

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