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French Drain System

The French drain is known by many names. It is also called the trench drain, filter drain, rubble drain, and rock drain, to mention a few. But regardless of what other designation it goes by, its function remains the same, which is to prevent excess water on the ground from puddling on or accumulating beneath the surface and causing damage.

Another interesting fact about French drains is its etymology. While it was most likely invented in France, this is not the reason why it is called a French drain. It was coined after Henry Flagg French, a US lawyer and agriculturalist who made it popular in one of his published articles in the 19th century.

pipes used in french drain

French Drains: Then and Now

With its long history and complicated etymology, you would be surprised at the simplicity of its process and how its design survived through time almost unscathed. Its earliest form as a plain ditch pitched on sloping ground and filled with gravel is not that much different from today’s iteration of the French drain.

The modern-day French drain still consists of the same sloping ditch filled with gravel, albeit with a few improvements. A perforated pipe is embedded within the gravel to facilitate water flow. The interface between the soil and gravel is also lined with landscaping fabric to filter out fine debris and soil particles.  The rudimentary form of the French drain, though, is still preferred and used by some even today, which is a testament to just how well it works

How do French drains work?

Water, by virtue of gravity, naturally flows downward through a path of least resistance. The French drain operates mainly through this simple principle. It encourages excess moisture to seep out of the surrounding saturated ground through its gravel and fabric, into the pipe, and out to wherever the discharge is pointed.

The bottom of the trench is given enough slope to allow water to flow into the exit, which is usually pointed to the drainage or a dry well, depending on the zoning laws or building codes in your area. They are especially useful in directing water away from certain areas where excess moisture is detrimental, such as a building’s foundation or the lawn.

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Collector drains generally provide temporary storage for ground water before being expelled into a safer place away from the house. Interceptor drains, on the other hand, capture water runoff on the surface before it reaches vulnerable structures such as a home’s foundation.

The French drain system has a simple design and concept, but there are still many ways that it can be installed differently. The curtain drain is one example of this variation. In this version of the French drain, a perforated pipe is also used to facilitate water flow

curtain drain

Over the years, the French drain has received many, albeit subtle upgrades. Continuous innovations in the agriculture and landscaping industry have benefited even the drainage system. The addition of filters in the system is among these minor but nonetheless effective changes.

The filter drain is another variation of the French drain system. It is built on the same simple design and concept-a perforated pipe embedded in gravel is used to facilitate water flow. The pipe, however, is laid down into a deeper trench compared to a curtain drain.

pathway and french drain
making an excavation

The ability of a French draining system to accommodate and successfully channel excess water that seeps in would depend not only on its design but its size as well. For a French drain to be effective, it must be sized properly. An alternative way to increase its capacity is the use of multiple pipes in a single trench.

How Are French Drains Installed?

The French drain system is a simple yet effective way to deal with excess water on the ground. Building it is also pretty straightforward.

  • Locate underground utilities

Before grabbing that trench digger, you must first locate all underground utilities such as pipes and cables for easy digging and to make sure none are damaged during the build.

  • Know your local zoning laws

Familiarize yourself with the zoning laws or local building codes to make sure you are not in violation of any rules, especially in choosing a location for your trench’s discharge point.

  • How to dig a trench

Find a part of the ground that slopes downhill to pitch your drain into. Alternatively, you can dig a sloping trench. A slope of one inch for every eight feet of the trench should be sufficient.

Prepare your trenching tool such as a trenching shovel or some garden hoes. A garden hoe is a surprisingly effective trencher to use.

Dig a trench 18 to 24 inches deep and five to six inches wide. If the French drain you are building will be integrated into an existing water-diverting system, you can dig a deeper ditch.

  • Initial layer of landscaping fabric and gravel

After digging, line the trench with landscaping fabric, preferably a continuous swath. Secure the fabric by driving staples through it into the ground then put some gravel over the fabric.

  • Laying the pipe

Lay the perforated or slotted pipe along the length of the trench, on top of the shallow layer of gravel. Make sure the holes are facing downward to keep the water level as low as possible. After this, fill the trench again with gravel almost to the level of the ground.

  • Finishing the work

Line the top surface of the gravel with another layer of landscaping fabric before finally covering with topsoil or sod.

The French drain can be installed with slight variations. Some opt to lay the pipe directly on the landscaping fabric then fill the trench with gravel all at once. Others choose the traditional French drain which is much cruder but still effective. Any of these variations will do as long as it does its job.

Application of French Drains

The simplicity of the process and design of the French drain does not diminish its effectivity. It has long been used in agriculture and landscaping but still finds many uses in today’s homes.

  • Protect the yard

The French drain is good for your yard if it usually gets flooded after heavy rain or becomes soggy with a lot of standing water. It can be installed to drain some of the excess water away from the lawn and into a safer place.

Standing water can cause the soil in your yard to turn muddy and make it unfit for foot traffic. In worse cases, it could become a breeding ground for mosquitoes and other insects that could bring diseases.

  • Protect the basement

Basement flooding is a common problem among homeowners. Poor drainage and sealing can cause water to enter your basement even with moderate rainfall. Hydrostatic pressure can push 

A French drain is an excellent solution to this problem. However, building it in a basement may not be as straightforward as doing it on the ground. You would be required to dig around the structure’s foundations or exterior walls, which could compromise a building’s integrity if not done properly. Also, your common garden tools such as broadfork and grub hoe would not do the trick.water from the saturated soil and into your basement through open cracks, holes, and porous surfaces.  

You would also need a sump pump to drain the water away and expel it into the storm drain, with the caveat to not connect the pump to the sanitary sewer. Aside from being illegal, it will overwhelm the sewage system. If you do not have extensive building or maintenance experience or the needed tools, have it installed by a professional.

  • Protect the retaining wall

A retaining wall is usually built with some form of a drainage system. However, it may not be enough to keep the higher ground from being flooded after a storm or heavy rain. A French drain is a good way to supplement the retaining wall’s drainage and get rid of unwanted groundwater faster.

  • To receive water from gutter downspouts

Water from your gutter downspouts should be drained a safe distance away from the house. A French drain dug beneath the exit of the gutter downspout is a good way to do this and protect your home’s foundations.

How Can We Help?

Digging near or around your home’s foundation with a grubbing hoe could get problematic. In addition, French drain installation, while simple, would still take time and effort. You should hire an expert yard drainage contractors to the job. We A-1 Drainage & Excavation  understand that, with the busy schedule of most homeowners, building the French drain is often not a top priority.

Let our team of professionals help. We can assess your existing draining system and recommend the best way to incorporate the French drain. Call us now and we would make sure that flooding, standing water, and muddy yards would be things of the past, the soonest time possible.