Which type of soil should you use for your septic drain field?

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Which type of soil should you use for your septic drain field?

26 October 2018
 Categories: , Blog


There are 3 important components that determine how effective your septic system is: the septic tank, drainage pipes and the drain field. Your drain field is perhaps one of the most important parts of the system.

After waste is treated within the septic tank itself, the drain field receives this treated waste and allows it to percolate to underlying soil layers. A clogged drain field is a common reason why your sewage system may back up into the home.

Here are 4 types of soil that can be used to prepare an effective drain field.

1. Sand 

Sandy soils are one of the best types of soils to use in septic tank drain fields. They consist of large and loose particles that provide enough space for wastewater to drain through.

The large pores in between sandy soils can hold larger waste particles while allowing finer particles to drain further down the soil layers. In this way, the drain field acts as a natural sieving agent for incoming waste. And because sand drains easily, blockages in the drain field are unlikely to occur.

Sand is also light and flexible. If you need to carry out maintenance on the drain field, you can easily dig up the sand and move it around as necessary.

2. Sand with a thin layer of clay 

Depending on the type of waste in your home, you may need a type of soil that doesn't drain too quickly. A slightly absorbent soil type separates waste better and "spreads the load" across the entire drain field. Rather than all the waste accumulating in underlying layers, upper layers of the soil can also hold some of the waste.

Sand, infused with a thin layer of clay, works well for this purpose. Sandy soils drain easily while clay is more compact and has fewer pores. The thin layer of clay can be used to cover up some of the pores inside loose sandy soils. This mixture also allows you to control drainage speeds and the overall texture of your soil.

3. Gravel 

Gravel, while not essentially a type of soil, can be used to create an effective drain field. Gravel particles drain easily, are light and flexible and don't retain foul odours on your property. You can add gravel to other types of soil so modify its texture, appearance and density. Furthermore, gravel can be easily installed or extracted from the drain field as necessary.

4. Loamy soils 

In some cases, loamy soils can also form an effective drain field. Loam is a balance between sand and clay, where it's not as light as sand and not as dense as clay. Loamy soils can treat effluent from the septic tank and remove harmful components before they reach underlying soil layers.