What's the difference between French Drain and Trench Drain?

Which one should you choose - French Drain or Trench Drains?

You might have seen different drains in your lawns and roads but do you really know what they do and which one you should choose for your drainage requirements? Do you have a drainage problem in your home or business? Or do you need installation of a french drain or a trench drain?

In this article, our expert plumber discusses the most common drainage solutions: trench drains, french drains and swales. Keep reading to learn more.

What are French Drains?

French drain system (also known as French ditch, land drain sub-surface drain, sub-soil drainage) is a trench filled with gravel or rocks. The trench consists of perforated pipes used to redirect surface water or groundwater from a specific area to a sewer or stormwater drains. It is often used to prevent water damage to retaining walls and building foundations.

Why install French Drains?

The gravel in these trenches acts as a filter which helps to remove the debris from the water. As this style of drain is placed deeper in the soil, they can draw out water efficiently and prevent soil erosion, protecting building foundations.

Water can often pool in your yard after heavy storms which can become a serious problem as it can cause issues like damage to retaining walls, allow water to leak into the lower areas of your home potentially weakening the building foundation.

If your home gets water run-off from your neighbours or have drainage problems, french drains can provide efficient yard drainage to handle excess water. They are commonly installed under the foundation wall on the external side of the foundation or underneath the basement floor.

Different types of French Drains

• Curtain drain - They are concealed by soil over which grass or plants can be grown. This type of French drain doesn’t extend to the surface.
• Filter drain - It drains groundwater.
• Collector Drain and Interceptor Drain - It drains groundwater as well as surface water and can be connected to the underground pipes to redirect surface water. They also have a cleanable filter to prevent clogged pipes
• Dispersal Drain - These drains are used to distribute the wastewater produced by a septic tank to the leach field.
• Fin Drains - They are narrow trenches and cheaper to build than traditional french drains. They consist of permeable membranes and can redirect groundwater and surface water to the drainage system.

History of the French Drain

French drains contrary to their name are actually invented by an American, Henry French in 1859. The earliest form of the french drain was designed as ditches sloped at an angle and consisted of gravel.

What is a Trench Drain?

Trench drains can also be called channel drains. In this drainage system, a long and narrow trench is constructed and covered with a grate. The grate can be made of plastic, metal, or precast concrete.

They are used to redirect surface run-off, stormwater, or surface liquids. They are used widely in residential, industrial, and commercial applications. For example, they can be used to collect food and beverage spills or chemical spills around restaurants or commercial buildings.

Another common type of surface drainage device is Swale. It is a broad and shallow ditch covered with vegetation. It is used to control the flow of water to prevent flooding, reduce the effect of drought, and limit soil erosion. Swale drains can be used in homes to collect stormwater from driveways or roofs and redirect the water to rain gardens. However swales are not appropriate for flat or steep landscapes.

Types of trench drains

• Cast-in-place - It is built using wood moulds and reinforced metal or stainless steel this type of trench drain can be labour-intensive and expensive.
• Former systems - These are like the cast-in-place trench drain wherein cardboard or lightweight expanded polystyrene is used instead of wood moulds.
• Pre-cast concrete - these drains are made in factories using polymer concrete.
• Linear Systems - Linear Drains are made from polymer concrete, fibreglass, steel or structural plastic.

What are the differences between a French Drain & a Trench Drain?

Trench drains are surface structures or above-ground drainage systems. They are used to redirect surface water to prevent soil erosion, water damage. However, French drains are underground or sub-surface drainage structures. French drains are used to capture and remove groundwater whereas trench drains are used to remove the surface water.

What type of drain do you need - French or Trench Drain?

If water is pooling on your yard or you have any surface drainage issue, trench systems need to be installed. However, if your retaining wall is getting damaged or you can see mould or structural damage in your home, it could be due to groundwater. In that case, it is best to install a french drain. It is also common to install both types of drain for efficient drainage.

Having trouble with your property drainage systems?

If you are having a drainage issue on your residential or commercial property, installing the appropriate surface or sub-surface drainage could resolve the issue. At Pure Plumbing Professionals, our expert plumbers can evaluate the problem and recommend the best solution. Contact us on 02 9191 7374 or complete our online job booking form.