French Drain vs Trench Drain vs Swale vs Slot Drains: A Complete Breakdown of Landscape Drainage Options


Landscaping is an art form in and of itself. Commercial landscaping especially is expected to look beautiful. But, landscaping does not end with the plants—there is also a great deal of care required to keep the landscape looking pristine.

One of the care requirements is ensuring that the landscape gets sufficient water and that any excess is properly drained. With that in mind, it is critical that you choose the right type of drainage system.

With so many options on the market, how do you know which one is best for your landscaping needs?

French Drains

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The French drain system is one of the oldest and most well-known drainage systems people still use today. Contrary to the name, it is not called a French drain because it comes from France, but because of who invented it: Henry Flagg French.

French created this system as a form of “farm drainage,” and it has become the basis of all modern-day systems.

When water flows through soil, it tends to take the path of least resistance. While it may occur slowly, it can have severe consequences as it saturates the ground entirely. If landscaping is around the perimeter of a building, the water may go toward the building’s foundation, finding its way into any cracks and getting into the basement level of the structure, which can lead to a whole host of issues including instability and mold.

This is where the French drain comes in. The French drain is a subsurface structure with the primary purpose of helping to divert water from the area where the drain is situated. French drains come with an underground barrier trench made with a gravel bed, which provides an easier route of travel for the water.

This barrier trench leads the water to a perforated pipe located at the bottom of the trench, where it goes to a connected outlet, such as a storm sewer, sump, irrigation cistern, or a swale.

Something to keep in mind about French drain systems is that the design has to accommodate for the natural flow of water, from the highest point in the ground to the lowest, for it to be effective.

Trench Drains

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Then there are trench drains, which commonly get confused with French drains. However, unlike French drains which are subsurface systems, trench drains are surface systems.

Trench drains, designed to intercept the flow of surface water runoff over vast expanses, are essentially a large trench with a heavy grate on top of it. This is the kind of drainage system that you find around commercial buildings, such as restaurants and loading docks. They help to keep the pavement around the trench drain dry, ensuring there is a minimal chance of a person slipping and falling.

While trench drains are inset into the ground, they are still technically considered a surface drain, meant to clear away water quickly. Underneath the drain’s grate, there is usually a plastic box that acts as a water transport system, taking the drained water and moving it towards a specified drain point.

Trench drains come in many different sizes, from incredibly broad, like what you may see around loading docks or city streets, to very thin, as you see on pool decks.

Swale Drain System

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Swale drain systems are lesser known systems that, like trench drains, are a surface system. However, swale drain systems are more broad and shallow in their construction, making them a more subtle option.

A swale drain is essentially a ditch that gets covered or lined with either turfgrass or other type of vegetation. The goal of a swale drain is to slow and control water runoff to prevent flooding, puddling, and soil erosion. It is also to help avoid overwhelming storm drain systems with an influx of water.

What makes a swale drain stand out from a regular ditch is that by being shallow, it slows down the spread of water runoff, allowing it to gradually filter into the soil on its own, which is less harmful to the surrounding landscaping.

For a more subtle drainage solution, swale drains are a great option to consider. They typically have a parabolic profile that starts from one edge and flows gently down, and then up. So, you could easily make an extensive one that looks as if it is part of the sculpting of the surrounding landscape.

Because of this, they are often used in both residential and commercial areas, and even in sustainable landscapes as a means of water conservation.

Slot Drain System

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Finally, there is the much newer Slot Drain system. This system is most similar to trench drains, but are always thin and barely noticeable. Because of their slim profile, they also eliminate the need for bulky, unsightly grates. Although it has such a thin profile, that does not mean it is any less effective than the other options on this list—it is capable of handling large amounts of water with no issue.

Slot Drain is incredibly durable and functional, with options for a wide range of applications, from inside food and beverage facilities to gardens and parks. They blend seamlessly with brick pavings, making them an ideal option for large parks, public patio gardens, plazas, and similar areas.

Making the Best Drainage Choice

Drainage systems are essential in many different situations, landscaping included. But, it is essential that you take the time to carefully consider your client’s landscape needs and designs so that you can choose the best and most effective option. They will want a reliable system that will last for many years and not have any issues when it comes to draining water runoff.

For more drainage information, contact a Slot Drain expert to talk about your project.

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