In fact, it may not be part of your indoor plumbing at all. Instead, your most important drain may be a trench filled with gravel and a perforated pipe in the landscape or next to your home's foundation. While you hardly see it, its role is essential to protecting your home from water damage.
This is the French drain, and if you've never heard of this essential drainage security measure, this website is designed to provide you with everything you need to know. A French drain, which may also be called a curtain drain, perimeter drain, weeping tile, or agricultural drain, is a gravel-filled trench that includes a perforated or slotted pipe. These drains are used to direct surface water or groundwater away from a specific area, such as a home's foundation.
French drains direct surface level water toward the lowest point and allow it to seep through the surface level gravel into the drain. This gravel also blocks the passage of excess debris.
The water is then collected in the perforated pipe, running at the base of the drain, and directed away from the home and toward a more suitable area for daylighting or infiltration. French drains differ from typical surface drains because they collect water over the entire length of the drain instead of one particular spot. French drains can also prevent water from collecting and pooling in specific areas, saturating the ground below, which may lead to water problems at the surface or below.
Instead, this water is directed to a more desirable location such as a dry well or an area of your choosing. Subsurface drainage systems have been in use for centuries, helping with everything from controlling agricultural runoff to providing yard drainage. They take many forms, but are all similar in design and function to the traditional French drain system. The earliest French drains were simple ditches filled with gravel. While many assume the origins of the French drain date back to France, the drain's name is actually believed to have come from former lawyer and U.
French used sections of roofing tile to create his own drains before later advancements included perforated drains to prevent clogging. Remember that liquid always seeks out the lowest point it can reach along the easiest path, readily moving into empty pockets in loose soil. That's the secret to a French drain: It provides a reliably easy path, creating a sunken channel that encourages water to percolate out of the surrounding soil and flow along a smooth course.
Gravity is essential for a French drain to function properly, as it first forces water down from the surface and out of saturated soil, then pulls it along the downward-sloping pipe to the desired discharge point.
One of the most common pipe materials used to create a French drain is plastic because of its durability. There are two frequently chosen pipe variations: corrugated and PVC.
Both are lightweight, but corrugated pipe can be flexible, while PVC is stronger and more rigid. Regardless of what the pipe is made of, it must be slotted or perforated at regular intervals to allow water to enter and flow through the system. Another option for areas that require French drain pipe installation is the EZflow system , which is a pipe that comes already surrounded by an aggregate and fabric mesh.
The drain pipe itself is made of high-density polyethylene, and is corrugated and perforated. French drain pipe alternatives such as this one are flexible and come in pre-set lengths, typically of 5 or 10 feet each. Considering other dimensions is also integral to installing French drain piping, as the pipe's diameter will impact how much water can flow through. A 4-inch diameter perforated French drain pipe is likely adequate for most residential applications, but areas expected to experience a good amount of water collection and heavy soil saturation may require a larger-diameter pipe.
Installing a French Drain There are two ways that a French drain can be built. French drain with perforated pipe: Work out where you would like the water to drain off to. Check the depth of the foundations of the building - the drain should be no deeper than the foundations of the building Plan the width of the drain - usually a width of mm wide is suitable, however this can vary depending on the property and how much water needs to drain. Fill the French drain - To prevent the drain getting clogged, you should line the trench with a water permeable fabric.
This fabric will prevent sediment build up and alleviate any water pressure that builds up. Make sure there is enough fabric left at the sides so that the fabric can be folded over the top of the drain. The French drain should be built like a large burrito. Imagine the fabric is the wrap and the pipe and aggregate are the filling. You should now fill the bottom of the trench with a layer of aggregate.
You should fill the trench to about a third of the way up. The larger the aggregate, the less likely blockages are to occur and the water will be able to flow through more quickly. The ideal size of aggregate used is around mm wide. Next, insert the perforated land drain pipe into the bottom of the trench. The pipe should be mm wide. Make sure that the perforated holes lay face down, if you lay the pipe any other way, the water will be unable to leave the pipe until it is full of water.
Half fill the trench with a layer of coarse gravel to just below the top of the trench. Fold over the layer of fabric to prevent any soil getting into the drain. Without perforated pipe: For a French drain without the landscape fabric and perforated pipe follow steps 1 to 6, as explained above.
Fill the French drain - Fill the French drain with aggregate. The water will flow through the gaps in between the individual pieces of aggregate. Cost of installing a French drain There are many factors that go into calculating the cost of installing a French drain. Permagard — French Drain Products at Low Trade Prices If you have any unanswered questions around French drains or their role in external waterproofing then call our technical team for free advice on Get the Job Done!
Add to Basket. Because there is a direct relationship between the diameter of a drain pipe and its relative effectiveness, make your trench no smaller than 12 inches wide, and aim for a depth between 18 and 24 inches. After digging your trench, fill it with a few inches of crushed stone. Cover the stone with water-permeable landscaping fabric to discourage weed growth. Next, lay piping into the trench. Choose one of two types, either rigid PVC with predrilled holes or flexible drain pipe cut with slits.
Flexible pipe, on the other hand, is less expensive and easier to work with. Opting for PVC? You can attach a degree angle joint to the start of your pipeline and then connect the joint to a pipe that can be left sticking out of the ground for an easy-access clean-out point. Another important thing to remember in PVC installations: Orient the pipe holes downward.
Counterintuitive though it may be, French drains work by allowing water to flow into them from below. You need to consider factors like:. Installation might involve temporary removal of structures like sidewalks and porches, and it could be dangerous work. Because of this, it is probably a good idea to let a professional handle the installation. Even an above-ground French pipe can become clogged and more frequently than one buried underground.
When the pipe clogs, you could unexpectedly wind up with a flooded basement. There could be soil erosion causing muddy water to enter the French drain, which can cause it to clog.
While you need to bury the drain deep enough, the groundwater passing through it can contain sediment that can build up. And, while at first the amount of this sediment won't be too much, over time it can clog the drain. You usually install a sump pump in the basement with an interior French drain to prevent or fix flooding. These types of drains are deeper in the ground. When a contractor handles the installation process, it's labor-intensive, requiring the digging of a large moat around the foundation of your building.
A bigger basement usually requires two sump pumps. A professional can install an exterior French drain around two to three feet underground so it can move surface water away from your home and property. The drain length will depend on how far away you would like the water released.
You can save yourself some money by installing the French drain yourself. Below are the steps you need to take to install your French drain. Evaluate the areas of your yard that are prone to flooding to determine a general route and location for the French drain. You'll want to decide where you want the water to flow and confirm the trench's drainage end or exit is in an ideal location.
Ensure your yard drainage won't negatively affect any public areas or anyone else's land, as this could cause legal issues. Ensure your plans comply with local law by checking with the building authority of your city.
You need to slope the French drain to carry the water down to the desired spot. If your yard has a steeper natural slope, this is OK, but the steepness increases the speed of the water, potentially leading to more erosion in the area the water exits. Drive a stake at the starting point and ending point of your planned trench route to check the natural slope.
Next, you'll:. Then, at regular intervals — around every four feet — measure straight down to the ground from the line to see the way the slope changes. If needed, adjust the trench's depth until you reach the desired slope.
Now, if it's necessary, you'll reset the level line and stakes so the line will run down the center of the trench you'll dig. Using a square garden spade, cut a line through the sod, ensuring it's straight, three inches to one side of the line to start digging your trench.
On the other side, you'll repeat the same process three inches from the line to create a six-inch-wide trench. Remove the sod and start digging, creating a sloped bottom and vertical sides. Your trench can be as deep as you want it. As you work, compact and smooth the trench's bottom.
Use landscape fabric to line the trench, using a continuous swath, if you can. If you can't, overlap fabric pieces by a minimum of 12 inches , and use fabric staples you'll drive into the ground with a hammer to secure the ends. Use the staples to secure both fabric ends. If there's excess fabric, fold it back to both sides of the trench, which you'll trim later on to fit it. Use coarse drainage gravel like crushed granite to fill the trench, so it's flush with the surrounding sod or ground.
Begin raking the top of the gravel to make it smooth and even it out with the top of your trench. Use a utility knife to trim the extra fabric along the edges.
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