What is Soak Pit? its 5 Functions, Design, Need & Advantages

A soak pit is a covered, porous-walled chamber that allows water to slowly soak into the ground and is also known as a soakaway or leach pit, and the pre-settled sewage from the septic tank is released to the underground chamber from where it infiltrates into the neighbouring soils.

A soak-pit is a closed porous chamber that is directly connected to a primary treatment unit of a commercial or residential building and slowly soak into the underlying ground it serves the function of letting the wastewater coming from the septic tank.

Design Considerations:

There are the following considerations for the design of a soak-pit such as;

1. It should be between 1.5 m and 4 m deep but as a general rule, never less than 2 m above the groundwater table.
2. From a drinking water source, it should be located at a safe distance ideally more than 30 m and it should also be kept away from high-traffic areas.
3. To provide support and prevent collapse, it can be left empty and lined with a porous material.
4. From collapsing, the rocks and gravel will prevent the walls but for wastewater, we will still provide adequate space.
5. A layer of sand and fine gravel should be spread over the bottom to help disperse the flow in both cases.
6. A removable lid should be used to seal the pit until it needs to be maintained to allow for future access.

Need for Soak Pit:

The water is not pure which is coming out from a primary treatment chamber and the primary treatment unit can be a septic tank, twin-pits, anaerobic baffled reactor, a biogas settler, etc. The effluent water which is coming out of these units is called greywater and before letting it into the ground soil this greywater must be subjected to a partial treatment.

Most of the wastewater management system needs a soak pit for this partial treatment and the partial treatment of effluent water through a soak-pit is a safer way of discharging the water into the surroundings.

Functions of Soak Pit:

To filtration, the greywater passing through the soak pit is subjected which results in the settlement of smaller particles of effluents at the bottom of the soak pit and by the microorganisms, these smaller particles are digested. Then through the porous wall of the soak pit, the filtered water is then discharged out.

There are some important functions of the soak pit as given below;

1. From the primary treatment unit, soak pit serves the purpose of receiving the effluent water.
2. It undertakes the partial treatment of the effluent water coming out of the primary treatment unit.
3. To the ground, the soak-pit discharges clear and non-harmful water.
4. The treated water comes out of the porous walls of the soak pit because of its design.
5. To recharge the groundwater bodies, the soak-pit helps.

Health Aspects:

As long as the immersion well is not used for raw sewage and storage/treatment technology is working well and health concerns will be minimum.

The humans and animals should not have contact with the affluent because the technology is located underground but it is important that the immersion well is located at a safe distance from a source of drinking water at least 30 m.

It must be accepted by even the most sensitive communities because the immersion well is odourless and is not visible.

Advantages of Soak Pit:

There are the following advantages of soak-pit such as;

1. With locally available materials it can be built and repaired.
2. For all users, the technique is simple to apply.
3. It requires a small land area.
4. The groundwater bodies are also recharged by it.
5. It has low operating costs and low capital costs.

Disadvantages of Soak Pit:

There are also some disadvantages of soak-pit as given below;

1. To prevent clogging, primary treatment is required.
2. It may negatively affect groundwater and soil properties.
3. In a cold climate, it is difficult to realize.
4. High daily volumes of discharged effluents, it should be avoided.
5. The areas where soil conditions allow infiltration and the groundwater table is at least 1.5 m below the soak pit then it is suitable.