During the spring months, as the weather starts to warm up and you want to start enjoying your backyard, you may be getting flashbacks of what your yard looked like in the fall and winter. You are most likely remembering that your space is unusable due to your yard being wet and muddy from accumulated surface water. To top it off, when the kids and pets come in from playing, they are always covered in wet grass and mud that gets tracked into your house. This can be super frustrating because you probably bought your house with the intention of actually using, and enjoying your yard! Luckily there is a fix. Putting in a French drain is the solution to drainage issues, effectively "waterproofing" your yard and will have you enjoying your backyard oasis in no time!
What is a French drain?
A French drain system is a trench, usually filled with soil, gravel or round rock, that contains a drainage pipe. Its purpose is to absorb ground and surface water, and make it disappear to a designated area.
French drains transport water away from yards, and are a great option for fixing a wet, soggy yard. By putting a French drain in your backyard, you can change what would otherwise be a damp spongy lawn, into a useable one by getting rid of all that excess water.
For a typical residential backyard, a French drain can cost anywhere between $5,000-$17,000.
A typical residential backyard is anything that takes 30 min or less to mow.
There are many different materials and methods that can be used to create a French drain. Each contractor designs and installs their system by using different materials, tools, and methods. This is the reason the cost of a French drainage system varies, and why some systems work better, and last longer than others.
The materials – Fabric, pipe, and backfill options when designing a French drain
Fabric (two options)
Single punched: This landscape fabric has half the number of punched openings as the double punched fabric, and can easily lead to clogging because it restricts the flow of water.
Double punched: This fabric has a high-water flow, and will not get plugged. It comes in different thicknesses for durability and lifespan.
Pipe (Three options)
Black ADS brand french drain pipe (Big-o, with lime green stripe): This pipe is made up of recycled materials and has three small inlets sliced in every valley. It is flexible and quick to install, but clogs and crushes very easily. It is the cheapest french drain pipe, and the most used pipe locally.
White PVC perforated pipe: This pipe is a rigid pipe that is 3x the price of big-o. It has no flex to it, does not stretch, and can crack when the ground settles. Due to each pipe being 10’ long, it is the slowest to install, because each of the 10’ sections have to be primed and glued together. Lots of fittings are needed to get the pipe to curve around trees or other objects. Unless it is installed below the frost line (18 inches) it will crack when frozen.
Blue High-Octane pipe (Baughman Tile brand): This purposed built French drainage pipe was designed for the clay soil that the Fraser Valley has. It is extremely flexible, fast to install, and has an excellent crush rating. Due to its 8 massive inlets in every valley, there is open air exchange that can dry out the subsoil much faster than any other option of pipe. Baughman tile is the most durable of all of the pipes, but is the most expensive option.
Back fill (Three options)
Existing soil: The trench drain can be backfilled using the existing soil that was excavated. This soil is usually clay, since yards with sandy soil do not typically need a drain put in. Using the native soil as backfill will work until the original soil compacts again. This gives you effective drainage for 2 months - 2 years.
¾” clear gravel: Backfilling the trench drain with gravel will allow some water to pass through, however, it only provides the trench with a little bit of void space. This lack of void space limits it’s storage potential in a heavy rain, or snow melt event, and never fully dries out the subsurface.
1 1/2” round rock:
When round rock is used to backfill the trench, it allows for greater void space and air movement, creating an underground drying effect. When the subsurface is dry, it allows the soil to act as a sponge, and soaks up water during rainfall. Plant roots are healthier, and your lawn will not have a yellowish waterlogged look to it.
The methods – How the trench, fabric and pipe can be dug and installed.
Amazingly, there are over 18 different combinations of methods that can be used by various contractors to build your French drain. The cost of a French drain installation is based on labor, tools needed to complete the job, and the effectiveness of the method used to install the French drain. Some systems will last centuries if the right materials and methods are used, while others can fail after only a few months after being put in.
The trench can be dug using two methods.
Digging by hand: When a trench is dug by hand this can be a very slow process, and due to it being so labor intensive, the proper depth may not be achieved.
Digging with an excavator:
Excavators are a way quicker way to dig a trench, and will be able to make it to the proper depth quicker than by hand. However, some space may not allow access for an excavator, and because excavated soil can expand up to 1.3 x its size, it can be nearly impossible to get the soil out of a yard unless the right machines are used. Skid steers or wheelbarrows can move the soil to a dump truck, where it can then be taken to be disposed of.
Fabric can be used in a number of ways in a French drain install. Its purpose is to keep soil from mixing with the rock around the pipe. Some contractors choose to use fabric, while others do not.
Not using fabric cuts down on the cost of installation. Without fabric in the trench, there is nothing from keeping the soil from penetrating into the pipe.
Fabric placed on top of the pipe:
When fabric is only placed on top of the pipe, the bottom and sides of the trench will allow soil to get into the gravel in the trench.
Fabric placed on bottom, sides and top of the trench:
When the pipe is “burrito” wrapped, no soil or debris can get into the system. By preventing soil and debris from entering the trench, there is no way that the pipe can get clogged, or backed up.
The Drain Pipe
The purpose of the pipe in a French drain system is to “carry” the water away from the area that is water logged. The placement of pipe really makes a difference in how the drain works, and for how long it will work for.
Placing the pipe on dirt: If the pipe is laid directly on top of the dirt, the inlets of the pipe can get clogged. Once the pipe is clogged, the system will not be able to work properly and the water will become stagnant.
Placing the pipe on rock: When the pipe is placed on top of the rock there will always be standing water under the pipe. If you have standing water, tree roots will seek out the water and infiltrate the system.
Placing the pipe on fabric: When the pipe is placed on fabric, it there is no clogging as the fabric keeps dirt and debris from getting into the trench. Since the pipe is at the bottom, there will be no standing water in the bottom of the trench.
There are over a hundred combinations of how a French drain can be installed.
This is due to the wide variety of different ways to combine all of the systems, materials and methods that can be used. It would be impossible to inform you of each type of install, so here are three typical installs we see. Usually, these French drains are based on price, ease of installation, and effectiveness.
Installation Method #1
Materials used: Big-o pipe
Method: The trench is hand dug, big-o pipe is put in, and clay soil backfills the trench.
Pros of this method:
- This option is the cheapest option because there are no disposal costs due to the original excavated soil being used to backfill the trench. No rock or fabric are used in this method, making the cost of materials go down.
- It is DIY friendly, as it is relatively easy to install. No excavators, skids steers or dump trucks are needed.
- Supplies are readily available at your local home renovation store.
Cons of this method:
- This method has a short lifespan of several months-2 years before clay soils around the pipe compact and don’t allow water to get to the pipe. Also, while this compaction is happening the pipe is becoming crushed and or filling with soil. Once the clay soil clogs the system, it is no longer serving its purpose as a drain.
- Since there is no rock put in with this method, there are no void spaces surrounding the pipe. Without void space, the subsurface will not dry out.
- Even though this method of install is the cheapest up front, in the long run it will be costlier when it needs to be dug up, disposed of, and redone. This means that your drain can double in price, costing you more than if you would have done a superior system up front.
Installation Method #2
Materials used: PVC pipe, 3/4” clear gravel, single punched fabric
Method: The trench is dug with an excavator, ¾” clear gravel is dumped into the trench, pipe is placed on top of the gravel, more gravel is used to backfill, and fabric is laid on top.
Pros of this method:
- PVC pipe will not crush like big-o
- This pipe has large inlet holes close to the bottom at the 5 and 7 o’clock mark.
- There is some void space around the pipe as ¾” clear gravel is used to backfill the trench. This method is superior than backfilling with dirt.
Cons of this method:
- This method is expensive compared to the big-o method due to the cost of installation and labor. PVC pipe is rigid, so if there are any curves around the existing landscape or trees that the pipe needs to curve around, it is time consuming to glue fittings on the pipe.
- Due to the pipe only having two holes on the bottom of it, its needs to be set on top of gravel so that the holes do not get clogged. This means that water will always be in the gravel below the pipe.
- The gravel under and around the PVC pipe will mix with the soil, as filter fabric is not used to encapsulate the entire French drain, just on top of the drain. This puts an expiry date on the system.
Installation Method #3
Materials used: Blue octane pipe (Baughman tile), double punched fabric, 1 ½” round rock
Method: This trench is dug with an excavator, double punched fabric lines the bottom, and sides of the trench, and blue octane pipe is placed inside. 1 ½” round rock is used as backfill, and the fabric burrito wraps the whole system.
Pros of this method:
- All of the materials and components involved in this method are rated for 200 years.
- The blue octane pipe (Baughman tile) has the largest inlets and numbers of holes in the pipe. The void spaces between the 1 1/2” round rock dry up the subsurface quickly, allowing your yard to be used sooner.
- Because the system is burrito wrapped, the soil cannot get into the trench, and will never clog. The tested filter fabric can pass 140 gallons per min of water, per square ft. allowing for optimal drainage, and the fabric will not slow down the water transfer.
Cons of this method:
- This method has the highest cost due to the materials (High Octane pipe, fabric, and rock) involved in making it, the removal of soil, and the rock used in backfilling the entire trench.
- Site access needs to be able to fit an excavator to dig the trench, and to allow for wheelbarrows and a skid steer to load dump trucks at the street.
- This system is not DIY friendly due to the amount of soil being hauled out, taken away, and rock being brought in to the site.
General price factors
Some factors that can increase the cost of your French drain install
- Putting down temporary plywood roads to protect surfaces from machinery
- Tight spaces that do not allow excavators, loaders and other machinery (resulting in the use of wheelbarrows, shovels, and hand digging)
- Obstacles that get in the way of the project (fences, trees, buildings)
- Disposal of materials (soil, old pipe etc.) and the amount of time driving and hauling these materials.
- Having to add a Sump system with electric pumps
- Length of distance to discharge station
- Tree roots (system may need extra pipe placed so that roots do not breach the pipe)
- Marking the area for utilities (Private utility contractor should be utilized when BC 1 call lists utilities in the area)
- What fabric, gravel and pipe are used in the system
- Size and length of the system (see diagrams below)
To give you an idea of how linear feet changes the size and price of a system, here are three examples of French drains being installed in the same yard, using the exact same materials. The more pipe that is installed, the greater the cost of the French drain will be due to labor and supplies. The plus side to this increase of pipe is that your system will dry your yard out faster after a rain event.
Some factors that can decrease the price of a French drain install
- New construction with no new landscaped areas
- Open site that allows machinery full access
- Onsite place to dispose of soil
To truly decide what system and methods are best for you, and your yard, you need to decide whether or not you want to solve your water problems for good. Having to redo the system in a couple of months-years is not only frustrating, but costly, as your old system will need to removed and hauled away, before a new one can be put in.
When a French drain system is done properly, the pain of the project is soon forgotten when you see your system working. Nothing beats having peace of mind that you put in the best French drain you can get.
To learn more, please visit the French Drain Man on YouTube.
Interested in learning more about French drains, check out our article on the Top Ten French Drain Problems.