While agricultural drainage lines are usually associated with farming, they can be used in residential settings to improve soil conditions, prevent flooding, and manage excess water. However, if the drainage line is improperly constructed, it can do more harm than good. To avoid such a scenario, let’s take a deep dive into the world of agricultural drains.

What is AG Drain?

Before we jump to the installation process, let’s first understand what AG drains are. 

Agricultural drains or lines refer to slotted PVC pipes installed within a trench filled with rocks or sand. These lines are primarily employed to facilitate the removal of excess groundwater. The trench allows the drain to collect water that seeps through the surface and transport it through the perforated PVC pipe. 

The idea of agricultural drains was introduced in the United States in the late 1840s and early 1850s, employing the Swap Land Acts of 1849 and 1850. It aimed at spurring economic growth by transforming the swampy regions in the Midwest into liveable areas. Large funds were allocated to promote drainage efforts by the federal government. 

However, later, the engineers began using these drains in residential settings to prevent flooding and improve soil conditions. 

Installation Process: The Nuts And Bolts of AG Drains

To fully benefit from ag drains, the installation of the ag lines needs your complete focus. The best way to install these pipes is:

Use Of Spoon Drains

It will be discussed later why Aggie drains should be a last resort, but for now, just know that if the water is already on the ground, use spoon drains. Water at the surface level should be managed at the surface. Aggie drains should be used for the water already present under the ground. 

Run Separate Pipes For Aggie Drainage

The agricultural drains should be connected to their own pipe system. Connecting Aggie lines to the stormwater systems is something you will regret for life. It may save you some bucks but will compromise the foundation of the building. 

Ensure The Right Direction Of The Flow

Make sure that the agricultural pipe and the trench are placed in the direction of the water flow. Water should be able to drain using gravity in the trench. 

Use Solid Pathways

The agricultural drains should not be positioned closer than 1 m from the house footings. For this first meter, you can use solid pathways or grade the ground away from the house. 

Use Unslotted Pipes

Only use unslotted pipes under your house. Slotted pipes will introduce more water and thus, will cause damage to the building’s foundation. 

Cap The Ag Pipe

One end of the Ag pipe should be brought to the surface and capped so it can be flushed from time to time.

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Use Slit Pits

The National Construction Code requires slit pits at certain positions. Make sure to keep the slits clean. 

To avoid any confusions, watch this demonstration.

Drainage Types

Drainage systems come in various types, each designed for specific purposes and conditions. However, two drainage systems are most commonly used worldwide. 

Surface Drainage 

In certain situations, when the aim is to prevent surface water from pooling and manage runoff effectively without harming the land, surface drainage emerges as an affordable and straightforward choice. This system removes the excess water from the soil surface by artificially sloping ground towards inlets, grassed waterways or shallow ditches. 

Subsurface Drainage 

This is a method used to remove excess groundwater or manage soil moisture beneath the earth’s surface. The system involves installing underground pipes or tiles designed in a way to efficiently collect and remove water from the soil. This prevents waterlogging and promotes healthier soil conditions. Subsurface drainage is mostly used in agriculture, construction and land reclamation to improve land usability. 

Slotted vs Unslotted AG pipes

Slotted and unslotted AG pipes are both used in drainage systems. However, they have distinct features and serve slightly different purposes. 

Slotted AG pipes

  • They are perforated with openings or slots along their length. 
  • The slots in these pipes allow water to enter the pipe from the surrounding soil or area making them more useful for subsurface drainage. 
  • As they help manage and alleviate water buildup, they are used in fields or areas prone to waterlogging.
  • They are the best choice for situations where you want to drain away water from the ground. 

Unslotted AG pipes

  • As apparent from the name, unslotted Ag pipes do not have perforations or slots along their length. 
  • They are typically used in surface drainage systems like open ditches. They channel water along the surface to a specific outlet. 
  • Unslotted Ag pipes are perfect for controlling surface water flow and preventing erosion. They direct water wherever you want without allowing it to enter any other pipe in the surrounding area.

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AG Drains Vs Trench Drains

Ag drains are built under the ground to manage the moisture level and water table. Whereas trench drains include long and narrow trenches built under the ground but covered with a grate on the surface. 

The main difference lies in the fact the ag drains are covered with soil and can not be seen from the surface. Whereas trench drains have a steel grate on the surface and are visible on the outside. You can find these drains in driveways, roadways and along sidewalks. 

Another difference is that trench drains are for surface water management while agricultural drains manage the underground water. 

Trench Drain

AG Drain

What’s The Best size Of AG Pipe To Use?

Ag pipes come in various diameters and choosing the right size is essential for effective drainage. However, to calculate the best size of Ag pipe, you will have to take various factors into consideration. Here are the most crucial ones:

Soil Type

Every type of soil requires different diameters and lengths of Ag pipes. For instance, coarse soils require larger pipes to facilitate water flow while smaller pipes will do well for finer soils. 

Drainage Intensity

The amount of water that is needed to be drained in a specific area is also a crucial factor. A higher drainage intensity requires larger pipes to handle the increased water volume. 

Drainage Depth 

The depth at which you want to manage the water table also impacts the choice of AG pipe’s size. Deeper drainage requires longer pipers with wider diameters. 

However, a general practice is that AG drains must be laid a minimum of 400mm into the soil and 100mm below any adjacent footing or pavement.

Checkout: Structural Engineer in Ipswich

When Does Agricultural Drain Become A Necessity? 

Agricultural drains should be the last resort when surface water management fails to improve the performance of your house drainage. 

To manage surface water, spoon drains are your best bet. While soakage trenches and agricultural drains should be employed when the water already present in the ground needs to be removed. 

These drainage systems should be used only when water is soaking into the ground:

  • Behind the retaining walls
  • Adjacent to the walls of the basement
  • Uphill from the house or running towards the house
  • Adjacent to deep footings

How Agricultural Drains Become A Curse For Homeowners?

Around 197 thousand houses were built in Australia in the year 2019, while approximately 178 thousand houses are forecasted to be built in fiscal year 2025. So, the amount of damage that can be done from improperly installed agricultural drains is huge. 

The irony with agricultural drain is that it can wreck the houses it was meant to protect. Let’s see how and why it happens. 

Agricultural drains are constructed to collect excess ground/surface water and transfer it to a far away outlet. However, it can become a homewrecker when instead of removing the water, it becomes the source of moisture. This happens when the ag pipes are not installed properly or installed too close to the foundation of the building. The long-term presence of water in these pipes can adversely affect the foundation and you may start observing cracks in the walls.

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So, How Do We Dodge This Bullet?

The easiest way is to never connect your ag pipes and stormwater pipes. But why?

Because every time it rains, the trench that was supposed to only collect and transfer a small amount of seeping water will be flooded with water from the roof downpipes. Thus, it will take longer to remove this water. The longer the water is going to stay in the trench, the greater will be the harm to the foundation. 

So, run separate pipes for agriculture drains and roof stormwater drains.

Concluding Thoughts

Construction can be life-saving and life-threatening at the same time. If small details are overlooked, it can lead to destruction on a large scale. Agricultural drains effectively protect your house’s foundation from moisture but only if they are installed in the right way. Any wrong decision during the construction can crack the foundation and lead to destruction. 

This article has covered everything you need to know about Agricultural Drains. Stay tuned to learn more!

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