French drains which, despite their name, originated in america, essentially work by providing invasive groundwater with a path of least resistance through which it can be redirected away from a structure or low-lying section of lawn. They’re named for a new Hampshire man, Henry Flagg French, who, in 1860, published a book with the intriguing title: Farm Drainage – The Principles, Processes, and Effects of Draining Land with Stones, Wood, Plows, and Open Ditches, and particularly with Tiles.
Nowadays, French drains are usually employed to combat flooding problems due to surface or groundwater which a property owner may be having, especially affecting their lawn, foundation or basement. They are also sometimes utilized to drain off liquid effluent from septic tanks.
The basic design, a gravel-filled trench, is straightforward however for it to continue working within the long term, it’s crucial that it be executed.
Flooding troubles are usually related to sloping ground, non-porous clayey soil, or a combination of the two. As an example, if your property is built over a slope along with your neighbors’ house occupying a great deal higher in the slope, heavy rainfall can precipitate an accumulation of groundwater rushing down using their property and on your own. If your soil is struggling to absorb all that water, you would likely experience harm to your house’s foundation, or leakage into a crawlspace or basement beneath the bottom floor of the home.
A linear French drain is a simple, inexpensive means to fix this type of problem. In this particular scenario, it behaves as a moat that protects your house by intercepting the groundwater rushing on the slope and directing it around and out of your house’s foundation.
A linear French drain is really a doable D.I.Y. project, if you don’t mind doing some backbreaking work (this may involve digging a trench, which after all is a thing closely akin to a ditch) and you have the appropriate tools and materials (1″ round washed gravel, 4″ PVC pipe with drainage holes, a trenching spade or power trencher along with a builder’s level)
So, let’s get right down to the nitty-gritty both how to build a French drain, and the way it works. First of all, you’ll need to dig an L-shaped or U-shaped trench system, 6″ wide and 24″ deep, 4 to 6 feet from your house. It’s important to not build the drain too near the house because, should you, you’ll be bringing water against the foundation, which is exactly what you don’t want.
The key leg in the trench system should be dug in the slope through the house. For a U-shaped French drain, it should be level and connected to two pipes on each side of the house with 90 degree PVC elbow joints. For an L-shaped drain, the key leg should slope down, in a pitch of at least 1/8 inch per foot of fall, for the second leg that will run alongside your house, also connected by means of a 90 degree PVC elbow joint.
When you find yourself designing your drain system, you need to make gravity work for you. Just like a river, groundwater flows downhill, so you’ll have to work with natural slope of your home and, when possible, hold the exit pipe come out above ground to give the groundwater a fairly easy exit point.
Once you’ve decided on the layout from the system and done the heavy work of digging the trenches, it’s time and energy to install the working areas of the drainage system: the gravel and pipes. To start with, tamp down any loose soil in the bottom from the trench and line it with 1 to 2 inches of gravel, lay the PVC pipes along with this primary layer of gravel, with all the holes pointing down, and after that fill out the trench with increased gravel, to one inch below ground level. Then all you need to do is cover the trench with sod or sdxgas decorative touch of your own choosing. And you’re done. The next time there’s a huge rain, excess ground water will enter your newly installed French drain and stay diverted around your home and discharged after the exit pipe or pipes.
It’s commonly suggest that a French drain be lined with geotech fabric as well as the piping be wrapped in a geotech sock to stop it from becoming clogged with silt. I don’t recommend doing either. Had you been going to use geotech fabric anywhere, the spot to set it will be along with the trench to prevent silt and sediment from filtering down from above and filling inside the air spaces between the gravel. A lot of the water that enters a French drain is groundwater flowing sideways underground, not downwards from the surface. Groundwater is not silty, it offers already had the silt and sediment filtered from it since it trickled down from the topsoil. If you doubt this, just think about whether underground spring water and well water are clear or muddy. Each of them are of course usually really clear because soil is really a natural water purifier.