What is Soak Pit | Estimate of Soak Pit | Design | Excel File Download

What is Soak Pit | Estimate of Soak Pit | Design | Excel File Download

A soak pit, also known as a soakaway or septic tank soakaway, is an underground structure designed to receive and disperse the effluent from a septic tank or wastewater treatment system. It allows the effluent to percolate into the surrounding soil gradually, promoting natural filtration and purification. Below, we’ll provide an overview of soak pits, estimation guidelines, and basic design considerations. Unfortunately, I cannot provide an Excel file download due to my limitations as a text-based AI model.

What is Soak Pit | Estimate of Soak Pit | Design | Excel File Download

Overview of Soak Pit:

A typical soak pit consists of a circular or rectangular pit, filled with loose aggregates like broken stones, gravel, or rubble. The effluent from the septic tank is discharged into the soak pit, where it infiltrates into the surrounding soil through the voids in the aggregates. The soil acts as a natural filter, removing impurities and contaminants from the effluent before it reaches the groundwater.

Estimation of Soak Pit:

Estimating the size of a soak pit depends on factors such as the capacity of the septic tank, the percolation rate of the soil, and the volume of wastewater generated. As a rough estimation, the soak pit size can be calculated using the following formula:

Soak Pit Volume = (Volume of Wastewater Generated per day) / (Percolation Rate of Soil)

Design Considerations for Soak Pit:

  1. Percolation Test: Before designing a soak pit, conduct a percolation test to determine the rate at which the soil can absorb the effluent. This test helps in selecting the appropriate size and depth of the pit.
  2. Pit Size and Depth: Based on the percolation rate and the volume of wastewater generated, calculate the required size and depth of the soak pit. Ensure that the pit is deep enough to avoid any surface overflow.
  3. Pit Structure: Use circular or rectangular concrete rings to construct the soak pit. Ensure that the rings are properly sealed to prevent seepage of effluent into the surrounding soil.
  4. Inlet and Outlet: Design the inlet and outlet pipes in such a way that the effluent is evenly distributed within the soak pit and that there is no backflow of untreated wastewater.
  5. Maintenance: Ensure easy access to the soak pit for periodic cleaning and maintenance. Regular desludging of the septic tank is essential to prevent the clogging of the soak pit.


Soak pits are essential for the effective treatment and disposal of wastewater from septic tanks. Proper estimation and design of soak pits are vital to ensure their efficiency and long-term functionality. It is crucial to adhere to local regulations and guidelines while designing and constructing soak pits to prevent any adverse impacts on the environment and groundwater quality. Consulting with a qualified civil engineer or wastewater treatment expert is recommended to design a soak pit suitable for the specific site conditions and wastewater treatment requirements.

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