Why Do We Need A Soak Pit for Our Home?

Each time we flush the toilet or wash so that down the sink’s drain,we create sewage

Kedalla Design and Construction (pvt) Ltd

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

What is A Soak Pit?

The waste water (greywater - personal washing, laundry, food preparation and cleaning of kitchen utensils or blackwater after primary treatment) generated in the house from kitchen, bathroom (the liquid waste of the household / Greywater) as well as WC (including human body waste - faeces + urine [Black water]) has to be disposed. If it is disposed in open it not only creates unhygienic conditions, foul odors but also invites epidemics and diseases (such as Cholera, typhoid, diarrhea, intestinal worms etc.).

So it is important to provide appropriate waste water management system in order to prevent pollution of surface water, ground water, flora & fauna, general environment and marine environment.

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A soakaway, soakage pit or leach pit

A soak pit, also known as a soakaway or leach pit is a covered, porous-walled chamber that allows water to slowly soak into the ground.

The first step in designing a soak pit is to determine the soakage rate of the natural ground. This is done by conducting a percolation test and, from the results of the test, determining the soakage rate.

The soak pit should be kept away from high-traffic areas so that the soil above and around it is not compacted.It can be left empty and lined with aporous material to provide supportand prevent collapse, or left unlinedand filled with coarse rocks and gravel. It should be located at a safe distance from a drinking water source

An ordinary pit of any shape

In Sri lanka, Each house owner constructed his or her soak pit and was made in charge of maintaining it. A soak pit is an ordinary pit of any shape. A soak pit can be built and repaired with locally available materials and a small land area is required. They are best suited to soils with good absorptive properties; clay, hard packed or rocky soils are not appropriate. The pit may be lined with stone, brick or concentrated blocks with dry open joints. The pit is generally filled with layer of loose stones, bricks bats and brick ballast. The pit may be covered with a RCC slab.

The treatment process

As waste-water (Effluent from domestic sources) percolates through the soil from the soak pit , small particles are filtered out by the soil matrix and organics are digested by micro-organism. They do not provide any direct treatment before entering the ground water table or other water body and the treatment process is much more efficient if the soil is kept well oxygenated.

A Soak Pit does not provide adequate treatment for raw wastewater and the pit will clog quickly. A Soak Pit should be used for discharging pre settled black water or grey water.

Soak pits are appropriate for

Soak pits are appropriate for rural and suburban settlements. They depend on soil with a sufficient absorptive capacity. They are not appropriate for areas that are prone to flooding or have high groundwater tables. Consulting engineers are able to provide site-specific design services appropriate in difficult locations and soil situations.

Lifetime of a soak pit?

For an average family, a well-sized soak pit should last between 3 and 5 years without maintenance. To extend the life of a soak pit, care should be taken to ensure that the effluent has been clarified and/ or filtered to prevent the excessive build-up of solids. s. If your soakage device is not working, this should be the first thing that is checked. Pay particular attention to the pipe work leading to the soakage device as this may be clogged independently of the device.

Why do we need a soak pit?

The waste water from the bathroom, kitchen etc (With high percentage of settleable solids) is directly connected to the soak pit. Ultimately the waste water in the soak pit will get absorbed by the surrounding soil. In a way, even if proper absorption area is available, the waste water will pollute the ground water and the untreated effluent may cause health hazards, nuisance and mosquito breeding..

Most of the sri lankan families built their own soak system by themselves and all the materials they needed could be gathered locally. Making the residents understand the health hazards of stagnant wastewater in front of homes was a difficult task, considering the low level of awareness and education, We "Kedalla" always try to explain how to install the systems and prepare necessary drawings for soak pits.

Do I need to evacuate my soak pit periodically?

Yes, if you are situated in water lodged area or size of the soak pit is not adequate or there are no. of soak pits surrounding your property or the strata of soil is impermeable, the soak pit would not be able to absorb the waste water. In such case the soak pit would over flow and the waste water would start getting collected on the ground. This would be hazardous from health point of view and also unpleasant and liable to cause epidemics.

Hence when such soak pit gets flooded and starts over flowing you have no option but to hire a tanker with pump (Generally made available by the municipality) to suck / pump out the waste water and empty the soak pit. They generally charge on hour or lump sum basis. In some areas, some privates also provides such services.

How often it needs emptying depends on a range of factors, from the size of the tank to the amount of waste that is added to the tank, and other variables. Some need emptying every couple of years, while others can go for decades before needing to be emptied. Your local specialist will help you plan this service.

Soakage pits shall be

We include easements in your site plan. There are many types of easements out there like right-of-ways, easements of support and even utility easements. We can show these graphically or with text. Using both is ideal; this way there's no question what easements exist on your site.

  • At least 18 m away from a well or other drinking water source
  • At least 5 m from the nearest building
  • At least 10 - 20 m from any other soakage pit
  • At least 1.5 m shall be kept between the bottom of the tank to the seasonal ground water table
  • Adequate contact area with the surrounding soil to absorb the effluent in to the soil. In clayey soil, larger pits will be needed
  • Adequate openings shall be left in the walls of the pit to have the contact with the surrounding soil

A considerable effect on the groundwater table

Effluent wastewater streams from industries are discharged into the soak pits and infiltrate into the surrounding soil. However, over discharge of effluent water into the soak pits have a considerable effect on the groundwater table.

Soak pits have known to cause contamination of ground water table due to percolation of effluents, into the aqua system, mostly through sandy or poor soils.

Determining the Size of the Soak Pit

Determining the size of soak pits isdependent on two things, theinfiltration rate of the soil and thequantity of waste water being put intoit. The infiltration rate of the soil canbe calculated by performing a perktest. The depth of a well-designed soakpit should be between 100 cm and 150cm. Increasing the depth of your soak pit will increase the storage capacity of your soak pit.

Performing a perk test

Soil tests are required to check that the soil on your property is capable of achieving the minimum percolation rate. A percolation (perk) test is a simple soil test that will help you determine the rate that water will infiltrate the soil. When the test is finished you will know a perk rate in the units of distance/ time (ex. 3 in/min or 1.5 cm/min). The test should be conducted by someone with the appropriate expertise

What if soakage is not appropriate for my property?

Soakage is not appropriate for your property if the percolation rate is less than 0.5 litres/min/m2.

You should consult a professional to discuss alternatives.

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Soakage Pit for Proper Disposal of Waste Water

Where a soak pit is required, a building consent application with calculations for soak pit sizing must be approved by the building consent authority (Pradeshiya Sabha / Municipal Council / Urbun Council)

Customer feedback has become the key to long-term growth. We collect customer feedback and use it to improve customer service.

Soakage pits are used to soak septic tank effluent in to the surrounding soil

"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