Why Do We Need A Septic Tank?

A septic tank can be used to treat the sewage from individual buildings at the building itself or for the whole community

Kedalla Design and Construction (pvt) Ltd

No:247 1/3
Peradeniya Road, Kandy (20000)
Sri Lanka

What is a Septic Tank?

Are you perhaps looking to purchase a piece of property? or planning a new home in your property? There are many things that go into the decision-making process when buying a piece of land or planning a home, but one of the most costly items in your new building will be your septic system (onsite sewage facility). There are many requirements for the proper placing of a system, the foremost of which is the type of soil on the site, and the presence of ground water.

Septic tank, sewage treatment and disposal unit used principally for single residences not connected to municipal sewerage systems. It consists ordinarily of watertight double-compartment concrete (fiberglass or polyethylene) tank buried in the ground. The tank receives wastewater from an inlet pipe (from all plumbing fixtures) and makes use of natural processes to treat the sewage it stores. Heavy solids settle to the bottom of the tank and are partially decomposed by anaerobic bacterial metabolism in the sludge (produces digested sludge and gases). Grease, oil and floating solids are blocked by a baffle board at the top of the tank (as scum /a crust over the liquid) as the effluent flows out into a drain field (or Soak Pit), from which it percolates downward into the ground. The tank should have an EFFLUENT FILTER at the outlet to keep solids from leaving the tank and clogging the leachfield.

After several years of use, the accumulated sludge must be pumped out of the tank for disposal at a municipal sewage-treatment plant. When properly designed, installed, and maintained, septic tanks and Soak Pits provide effective long-term, low-cost, on-site wastewater disposal.

Where does the septic tank require?

Normally in well planned cities the municipal infrastructure will have centralized sewerage network where you can connect the waste water to the municipal sewerage system. Hence if it is present there is nothing to worry.

However, when the municipal sewerage system is absent, In rural, urban and semi-urban areas where adequate water supply is available from the pipe but not engaged proper sewer system, hence the septic tank is suitable for disposal of sewerage in those areas and It is an individual or family sanitation system. In septic tank effluent from WC is collected. The effluent here gets treated biologically and the treated water will then be connected to the soak pit.

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Approval to construct and approval to use a septic tank system

An application for approval to construct a septic system must be made to the local government(Pradeshiya Shaba / Minucipal Council or Urbun Development Authority). This approval permits the system to be constructed only, not used.

It is an offence to commence construction of a wastewater system without an approval. Before it can be used, the local government must inspect the system to ensure it is installed correctly. If satisfactory, the local government will issue an approval for the system to be used. It is an offence to commence using the system prior to receiving the local government’s approval (certificate of conformity).

Proper Installation

Have your septic system installed properly to avoid problems down the road?As we discussed, When you apply for a building permit, health officials in your area will visit your building site to confirm that the ground will support a septic system. They will verify that the property has the conditions required for a nonproblematic septic system.

Recent innovations in septic tank systems

Septic system design and size can vary widely, from within your neighborhood to across the country, due to a combination of factors. These factors include household size, soil type, site slope, lot size, proximity to sensitive water bodies, weather conditions, or even local regulations.

Septic tank systems are now available in lightweight materials such as plastics and fibreglass and can also come in disassembled components for ease of transport. Another development is the use of filters on the outlet of septic tanks which reduces the amount of solids in the outgoing effluent.

Septic tanks are good for the environment

Septic tanks eliminate waste by using the natural filtering process of the soil. Wastewater is first filtered by the septic tank before ending up in the leachfield or drainfield. Bacteria is filtered by the soil once the wastewater is out of the septic tank, which makes the water safe to re-use. The use of septic tanks allows for local water tables to be naturally replenished. Local water tables benefit the wildlife in the area and septic tanks contribute to this cycle by recycling wastewater.


The drainfield is where liquid from the septic tank flows through pipes in your yard for final treatment by organisms in the soil. Grass and/or shallow-rooted plants are the best covers for your drainfield.

Drainfield failure

Solids that are not decomposed remain in the septic tank. If they are not removed by periodic pumping, solids continue to accumulate until they over-flow into the drainfield. This eventually leads to drainfield plugging and drainfield failure.

Desludging of septic tank

If the septic tanks accumulate too much sludge and scum, the effective volume of the tank is reduced which in turn reduces the time for separation to take place. This means not all the solids, grease and oils will separate and will pass out of the septic tanks and into the drainfield or soakage pit. To prevent this from happening, it is necessary to have the septic tanks desludged (pumped out) regularly.

The desirable frequency of desludging is dependent on the number of people contributing to the wastewater load. As a guide, every eight years for a two-person household, every four years for a four-person household and more often for households with greater numbers, is recommended.

Septic tank maintenance

Buried beneath your back yard, it is out there—constantly working. When you’re at work, it is working. When you’re eating dinner, it continues working. And when you’re sleeping, it’s still out there in the dark—working. What is it? Your septic system. It may be the most overlooked and undervalued utility in your home; but with proper care and maintenance, your septic system can continue to work for you for at least 25 to 30 years.You can do a few things regularly to keep your septic tank and system running smoothly. Check faucets and toilets for leaks and make repairs if necessary. Crawl under your house periodically or look in the basement, if you have one, to check for additional leaks.

Solids must always be pumped from the tank eventually. When the bottom of the scum begins collecting within three inches or so of the outlet, or when the top of the sludge is within 12 inches, it's time. Check the status of the situation at least once a year.

Your septic tank can last as long as your home will if you maintain it. You can use your septic tank for up to forty years and even more if you have a professional inspect and maintain it regularly. You need to look for a professional who can service your septic tank whenever needed to prevent damages and clogs.

Preventing groundwater pollution

Preventing groundwater pollution from failing septic systems should be a priority for every community and every homeowner. Contamination of the groundwater source can lead to the pollution of local wells, streams, lakes, and ponds — exposing family, friends, and neighbors to waterborne diseases and other serious health risks.

When a septic system fails, inadequately treated domestic waste can reach the groundwater. Bacteria and viruses from human waste can cause dysentery, hepatitis, and typhoid fever. Many serious outbreaks of these diseases have been caused by contaminated drinking water.

Three main reasons for septic system maintenance

There are three main reasons why septic system maintenance is so important. The first reason is money. Failing septic systems are expensive to repair or replace, and improper maintenance by homeowners is a common cause of early system failure.

The second and most important reason to properly maintain your system is the health of your family, your community, and the environment. When septic systems fail, inadequately treated household wastewater is released into the environment. Any contact with untreated human waste can pose a significant risk to public health.

A third reason to maintain your septic system is to maintain the economic health of your community. Failing septic systems can cause property values to decline. Sometimes building permits cannot be issued for these properties. Also, failing septic systems may contribute to the pollution of local rivers, lakes, and shoreline that your community uses for commercial or recreational activities.

What not to flush

By educating everyone in your household about what is and what isn’t good for septic systems, they can begin to develop good maintenance habits.

What you put into your septic system greatly affects its ability to do its job. Remember, your septic system contains living organisms that digest and treat waste. As a general rule of thumb, do not dispose of anything in your septic system that can just as easily be put in the trash. Your system is not designed to be a garbage can and solids build up in the septic tank that will eventually need to be pumped. The more solids that go into the tank, the more frequently the tank will need to be pumped, and the higher the risk for problems to arise.

Don't use the toilet to dispose of plastics, paper towels, facial tissues, tampons, sanitary napkins, cigarette butts, dental floss, disposable diapers, condoms, kitty litter, Unwanted medications or large amounts of disinfectant (biocides) or other strong chemicals etc. These can kill the normal bacteria and interfere with the system. The only things that should be flushed down the toilet are wastewater and toilet paper

When used as recommended by the manufacturer, most household cleaning products will not adversely affect the operation of your septic tank. Drain cleaners are an exception, however, and only a small amount of these products can kill the bacteria and temporarily disrupt the operation of the tank.

What about disused systems?

If a property that has a septic tank is then connected to a sewage system, the disused septic tank will ultimately require decommissioning. This entails pumping the contents out of the tanks preferably followed by removal of the system. If removal is not possible due to the base of the impervious tank being broken, the entire system (tanks, leachdrains and soakwells) must be backfilled with clean soil.

Tips for a healthy efficient septic tank system

  • Have the septic tanks pumped out regularly.
  • Allow as little fat or grease as possible into the system.
  • Regularly switch the drain or soakwells in use if you have an alternating system.
  • Do not drive vehicles over the system.
  • Do learn the location of your septic tank and drainfield. Keep a sketch of it handy with your maintenance record for service
  • Do have your septic system inspected annually
  • Do keep your septic tank cover accessible for inspections and pumping. Install risers if necessary.
  • Do call a professional whenever you experience problems with your system, or if there are any signs of system failure.
  • Do keep a detailed record of repairs, pumping, inspections, permits issued, and other maintenance activities.
  • Do conserve water to avoid overloading the system. Be sure to repair any leaky faucets or toilets.
  • Do divert other sources of water, like roof drains, house footing drains, and sump pumps, away from the septic system. Excessive water keeps the soil in the drainfield from naturally cleansing the wastewater.

How to deal with septic tank system

  • Don’t go down into a septic tank. Toxic gases are produced by the natural treatment processes in septic tanks and can kill in minutes. Extreme care should be taken when inspecting a septic tank, even when just looking in
  • Don’t allow anyone to drive or park over any part of the system.
  • Don’t plant anything over or near the drainfield except grass. Roots from nearby trees or shrubs may clog and damage the drain lines.
  • Don’t dig in your drainfield or build anything over it, and don’t cover the drainfield with a hard surface such as concrete or asphalt. The area over the drainfield should have only a grass cover. The grass will not only prevent erosion, but will help remove excess water
  • Don’t make or allow repairs to your septic system without obtaining the required advice
  • Don’t use septic tank additives. Under normal operating conditions, these products usually do not help and some may even be harmful to your system
  • Don’t use your toilet as a trash can or poison your septic system and the groundwater by pouring harmful chemicals and cleansers down the drain. Harsh chemicals can kill the beneficial bacteria that treat your wastewater.
  • Don’t allow backwash from home water softeners to enter the septic system

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Keep Your Septic System Healthy

To keep your septic system healthy, you need to make sure that only the right kinds of elements enter the system

Providing excellent customer service is an ongoing process of our business,

The purpose of a septic tank is to retain sewage so that it is given time to be liquefied by the action of Anaerobic Bacteria

"Kedalla is an ideal place for house planning in Kandy area. They are expert in that field. Creative and reliable. Explained all the facts in friendly manner and everything is fair. Trusted service. You planned our future shelter the best. We wish you all the best. Welldone "Kedalla"

Mr.A Edirisinghe

Deputy Principal

Vidyartha College, Kandy