What is soak pit and why is it important?

A soak pit is an essential part of any home drainage system. It helps in collecting and disposing of wastewater safely away from the house. By utilising a soak pit, you can reduce the amount of contaminated water being released into the environment and help to maintain cleanliness around your property. 

The soak pit also serves as a natural filter for pollutants that may be present in the wastewater. Additionally, the soak pit helps reduce odours that may be caused by wastewater accumulation. 

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What is a soak pit?

A soak pit, also known as a soakaway or leach pit, is a covered, porous-walled chamber that allows water to infiltrate slowly into the ground. It is an essential component of a home’s drainage system, facilitating the safe disposal of wastewater from sources such as kitchens, bathrooms, and washing areas. By directing wastewater into a soak pit, contaminants are filtered naturally through the soil, reducing environmental pollution and maintaining cleanliness around the property. Additionally, soak pits help mitigate odours associated with wastewater accumulation.

 

How does a soak pit work?

A soak pit typically consists of a chamber, often circular or rectangular, featuring regularly spaced pores. It is connected to the septic tank through a wastewater pipe that carries effluent from various sources like toilets, kitchens, and bathrooms. Within the pit, boulders and gravels are placed to facilitate the filtration of water and organic materials present in the effluent.

The effluent entering the soak pit undergoes a filtration process, wherein smaller particles and organic matter settle at the bottom of the pit. These tiny particles are subsequently decomposed and consumed by microorganisms. The filtered water then gradually permeates into the surrounding soil. Soak pits are most effective in areas with permeable soils exhibiting a high absorption or infiltration rate.

 

Soak pit: Advantages

• Use of locally available materials for construction.
• Simplicity in construction and operation, making it accessible for anyone.
• Requires a small installation area.
• Facilitates groundwater table replenishment.
• A power-efficient and sustainable technique.
• Particularly suitable for rural areas lacking municipal drainage systems.
• Economical, with a low initial capital investment, making it affordable for all.

 

Soak pit: Should you clean it regularly?

It is essential to clean your soak pit regularly. Depending on the size and use of your septic system, you may need to evacuate your soak pit every few months. The frequency will depend on how heavily the system is being used and what types of materials are being disposed of in the system. 

As a best practice, if the system is regularly receiving large quantities of water, it is recommended to evacuate the soak pit at least every two to three months. If you notice any signs of malfunction or backup in your septic system, it is important to evacuate the soak pit sooner rather than later. This will help prevent any further damage and keep your system functioning properly. A professional should be consulted to inspect your system on a regular basis and provide any necessary servicing or repairs.

It’s also important to note that when evacuating the soak pit, all the contents should be disposed of in an approved manner. If in doubt, contact your local public health authority for more information on how to properly evacuate and dispose of wastewater from a soak pit.  

Soak pit: Ideal location 

The soak pit should be located at a safe distance from drinking water sources (ideally more than 30 meters) to prevent contamination. It should also be situated away from high-traffic areas to avoid soil compaction, which can lead to clogging. Additionally, the soak pit should be positioned at least 2 meters above the highest groundwater table to prevent groundwater contamination.

Soak pit: Size and depth 

Generally speaking, it is recommended that the pit should have a minimum depth of up to 4 metres. It is also important to ensure that the pit is not deeper than the water table of the region. Otherwise, it may fill up with groundwater, reducing its capacity and effectiveness. 

The depth of the soak pit should be dug in such a way that there are no sharp turns or inclines to reduce turbulence and allow for a uniform inflow of runoff. The pit should also be lined with a porous material, such as gravel or sand, to reduce the flow velocity and allow for maximum infiltration rate. 

It is also important to ensure that the outlet pipe of the soak pit is positioned at an appropriate elevation to prevent the backflow of water into the pit. Finally, it is recommended that a protective layer should be spread over the top of the pit to reduce erosion and protect its integrity. You can ensure that your soak pit is properly constructed and will effectively absorb runoff from your property. 

Soak pit: Maintenance tips for a home soak pit 

Regular cleaning

Regular cleaning is essential to ensure your soak pit is working properly. To clean the soak pit, use a spade to remove any accumulated silt or debris from the bottom and around the edges of the tank. Carefully inspect all components, such as risers, manholes and outlets, for damage or blockages. 

Disposing of the water properly 

Be sure to properly dispose of any water that has been drained from the soak pit. Never let it flow into a nearby water source, as this can have damaging environmental consequences. Instead, dispose of it in an approved septic tank or drain field where it can be broken down safely and efficiently. 

Avoiding clogging or blockage of the soak pit 

To avoid clogging or blockage of the soak pit, it is important to be mindful of what goes into it. Never pour paint, oil, grease or other hazardous chemicals down your soak pit as these can damage the filtering system and cause contamination. Also, try to reduce the amount of solid waste that enters the soak pit, such as food scraps, paper towels and diapers, by using a sink strainer or other type of filter. 

Regular inspection 

To ensure your soak pit remains in good working order, it is important to have it inspected regularly by a professional. An annual inspection can help catch any potential issues before they become more serious, allowing you to make repairs quickly and easily. 

 

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Common issues and troubleshooting

Over time, soak pits may encounter issues that can affect their efficiency:

• Clogging: Accumulation of solids and organic matter can lead to reduced infiltration rates. Regular maintenance, such as removing sludge and preventing the entry of non-biodegradable materials, can mitigate this issue.

• Odor Problems: Unpleasant smells may arise from improper decomposition of organic matter. Ensuring adequate ventilation and avoiding the disposal of grease or oils into the system can help prevent odors.

• Overflowing: This can occur if the soak pit is undersized or if there’s an unexpected increase in wastewater volume. Regular monitoring and adjusting the system’s capacity as needed are crucial.

Addressing these issues promptly through proper maintenance and consultation with professionals can prolong the lifespan and effectiveness of the soak pit.

Integration with other wastewater management systems

Soak pits are often part of a broader wastewater management strategy:

• Septic Tanks: Pre-treated effluent from septic tanks can be directed to soak pits for further filtration and absorption into the soil.

• Greywater Systems: Soak pits can handle greywater from baths, kitchens, and washing machines, reducing the load on primary treatment systems.

• Rainwater Harvesting: In some designs, soak pits can be integrated with rainwater harvesting systems to manage stormwater runoff, thereby recharging groundwater levels.

Design considerations for soak pits

When planning a soak pit, several factors should be taken into account:

• Soil Permeability: Soak pits are most effective in soils with good absorptive properties. Clay, hard-packed, or rocky soils are not appropriate, as they hinder the infiltration process.
  

• Pit Dimensions: The soak pit should be between 1.5 and 4 meters deep, but as a rule of thumb, never less than 2 meters above the groundwater table. Its bottom should never be less than 2 meters above the groundwater table. The pit should have a cross-sectional area of approximately 1 square meter. The dimensions may vary based on the volume of wastewater to be managed and the soil’s absorption capacity.

• Construction Materials: The soak pit can be left empty and lined with a porous material to provide support and prevent collapse, or left unlined and filled with coarse rocks and gravel. The rocks and gravel will prevent the walls from collapsing while providing adequate space for the wastewater.

Alternatives to soak pits

In areas where soil conditions are unsuitable for soak pits or where groundwater contamination is a concern, alternative wastewater management solutions can be considered:

• Constructed Wetlands: These systems use natural processes involving wetland vegetation, soils, and their associated microbial assemblages to treat wastewater.

• Sand Filters: Sand filtration systems can effectively treat wastewater by removing contaminants through physical and biological processes.

• Evapotranspiration Beds: These systems rely on the combined processes of evaporation and plant transpiration to dispose of wastewater, making them suitable for areas with high evaporation rates.

Environmental impact of soak pits

While soak pits are effective for wastewater management, their environmental impact requires careful consideration. Improperly designed or maintained soak pits can lead to groundwater contamination, posing health risks. To mitigate this, it’s essential to ensure that soak pits are constructed at least 2 meters above the highest groundwater table and located more than 30 meters away from drinking water sources.

Housing.com POV

Soak pits are a practical and eco-friendly solution for managing household wastewater, especially in areas without centralised sewage systems. They facilitate natural filtration and groundwater recharge, highlighting their environmental significance. However, the effectiveness of a soak pit depends on meticulous design, appropriate site selection, and consistent maintenance. Neglecting these aspects can lead to groundwater contamination and system inefficiency. Therefore, while soak pits are valuable components of sustainable wastewater management, they require informed planning and diligent upkeep to function optimally.

FAQs 

Where should I place my soak pit?

The ideal location for a soak pit should be away from underground or surface water sources to prevent wastewater from seeping into them. It should also be located far enough away from sewage collection systems and septic tanks so that it does not clog them up.

What is the size and depth of a soak pit?

On the whole, it is advised that the pit have a minimum depth of up to 4 metres. Additionally, it is crucial to make sure the pit does not go much deeper than the area's water table.

How do I maintain my soak pit?

The soak pit must be cleaned and inspected frequently to remain in good operating order. Additionally, stay away from adding solid trash or dangerous chemicals to the soak pit, as this can clog the system. Empty any water from the soak pit into a drain field or septic tank that has been permitted.