Soak Pit and Soak Holes Explained

soak pit and soak holes explained

In New Zealand, particularly in our vibrant city of Auckland, we're no strangers to managing water, especially stormwater. It's a task as necessary as it is intricate, demanding a good understanding of various systems and methods. Today, we'll shed some light on two of these systems - soak pits and soak holes, their workings, differences, benefits, and how they compare to septic tanks. Understanding these systems will help us effectively manage stormwater and contribute to the overall well-being of our environment.

Here at Real Drainlayers, we're always asked about the differences between soak holes and soak pits, how they work, what the benefits of each are, and more. Needless to say, we've spent a lot of time answering questions regarding soak holes and soak pits.

To better help you understand the differences and the benefits, we'll delve into the specifics of each system, highlighting the unique characteristics that make them suitable for different applications. Along the way, we'll explore the various regulations and guidelines that govern their use in New Zealand. By the end of this article, you'll have a solid understanding of soak pits and soak holes and their role in maintaining a sustainable water management strategy.

What is a Soak Hole?

A soak hole, often called a soakaway, is a type of drainage system designed to manage stormwater or surface water on a property. It's essentially a hole dug into the ground, filled with coarse stone or rubble, allowing water to percolate into the surrounding soil. They're a common feature in New Zealand's residential and commercial properties, particularly in areas with limited stormwater reticulation.

Soak holes are versatile and can be adapted to various site conditions, making them a popular choice for property owners. They're not only functional but also contribute to the overall aesthetics of the property by managing excess water and preventing unsightly puddles or waterlogging. By effectively managing stormwater, soak holes play an essential role in maintaining the health of local ecosystems and reducing the impact of urban development on the environment.

How does a soak hole work?

Similarly to a cesspit, soak holes work on the principle of gravity and percolation. When rainwater collects on your property - whether from your roof or other surfaces - it needs somewhere to go. With a soak hole, this water is directed into the hole, where it then slowly seeps or 'percolates' into the surrounding soil. This mechanism helps to manage the volume of stormwater, reducing the risk of flooding and waterlogging on the property.

The effectiveness of a soak hole largely depends on the characteristics of the soil in the area. Soils with higher infiltration rates, such as sandy or gravelly soils, are better suited for soak holes, as they allow water to seep through more quickly. Conversely, soils with low infiltration rates, such as clay or silt, may not work as well with soak holes, as they may take longer to absorb water or become saturated, leading to potential issues with stormwater management.

Soak Pit vs Soak Hole - What's the difference?

While the terms "soak pit" and "soak hole" are often used interchangeably, there are subtle differences. A soak pit is typically a covered, man-made pit filled with layers of rocks or porous material, and it is designed to disperse excess water into the ground. A soak hole, on the other hand, can be a natural or man-made depression in the ground where water collects and is absorbed.

The primary difference between the two lies in their construction and intended purpose. Soak pits are generally more structured and built with specific materials to facilitate water percolation. They are often used in urban settings or areas where controlled drainage is required. Soak holes, while similar in function, can be less formal and may occur naturally in the landscape. They are more likely to be found in rural settings or areas with less stringent stormwater management requirements.

What Are The Benefits of a Soak Pit?

Soak pits offer several benefits. They help manage stormwater, reducing the risk of flooding on your property. This role is crucial, especially in areas with high rainfall or inadequate public stormwater infrastructure. By preventing water buildup, they contribute to maintaining the structural integrity of buildings and other structures on the property.

Furthermore, soak pits provide an avenue for rainwater to percolate into the ground, thus helping to recharge groundwater levels. This natural replenishment of groundwater is essential for maintaining the health and sustainability of local ecosystems. In addition to their practical benefits, soak pits are also relatively easy to construct and maintain, making them a cost-effective solution for many property owners.

What is The Difference Between a Septic Tank and a Soak Pit?

While both septic tanks and soak pits serve to manage water, they are designed for different types of water. A septic tank is a part of the wastewater treatment system, designed to manage sewage from a property. The waste goes into the septic tank where solids settle, and the remaining liquid is treated and discharged.

On the other hand, a soak pit is designed to manage clean water, such as rainwater or surface runoff. It is not designed to handle sewage or wastewater. While a septic tank treats and discharges water, a soak pit simply allows water to soak into the ground. Both systems play vital roles in managing water on a property, but they serve very different functions and should not be used interchangeably.

What Are The Requirements For a Soak Pit NZ?

In New Zealand, particularly in Auckland, there are specific requirements for installing a soak pit. The Auckland Unitary Plan provides guidelines for the design and construction of soak pits. These guidelines include:

  • The soak pit should be designed to manage a 10% Annual Exceedance Probability (AEP) rainfall event, with sufficient freeboard to contain a 2% AEP event without overflow.
  • The soak pit must be located at least 5 meters from any building, 1 meter from any boundary, and above the highest known groundwater table.

These regulations are designed to ensure the safety and effectiveness of soak pits in managing stormwater. But the rules don't stop there. They continue:

  • The soak pit must be filled with hardfill material, such as clean crushed rock.
  • The dimensions of the soak pit - depth, diameter or width - should be based on the soil's infiltration rate, which can be determined through a soakage test.
  • If the soak pit is deeper than 1.5 meters, it must be designed by a Chartered Professional Engineer.
  • The soak pit must be covered and secured to prevent any accidental falls or entry of debris.

All these requirements aim to ensure that soak pits function optimally while ensuring safety. Non-compliance can lead to ineffective stormwater management, potential legal issues, and even structural damage to nearby buildings. It's always advisable to work with a professional when installing a soak pit to ensure that it meets all the necessary requirements and functions effectively.

In conclusion, soak pits and soak holes play a critical role in stormwater management in New Zealand. While they serve similar purposes, they are distinct in their design and application. Understanding these systems and the regulations that govern them is essential for any property owner or developer. Always remember to consult with a professional drainlayer or engineer - like those provided by Real Drainlayers - to ensure your soak pit or soak hole is designed and installed correctly, and is compliant with all relevant standards and regulations.

 

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