French drains which, despite their name, originated in the United States, 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 are 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 Outcomes of Draining Land with Stones, Wood, Plows, and Open Ditches, and particularly with Tiles.
Nowadays, French drains are generally utilized to combat flooding problems due to surface and/or groundwater which a property owner could be having, especially affecting their lawn, foundation or basement. They are also sometimes used to drain off liquid effluent from septic tanks.
The essential design, a gravel-filled trench, is simple but also for it to go on working on the long run, it’s important that it be well executed.
Flooding troubles are usually connected with sloping ground, non-porous clayey soil, or a combination of both. As an example, if your property is constructed on the slope together with your neighbors’ house occupying a lot higher up the slope, heavy rainfall can precipitate an accumulation of groundwater rushing down off their property and on to your own. If your soil is struggling to absorb all of that water, you would likely experience injury to your house’s foundation, or leakage into a crawlspace or basement beneath the bottom floor of your home.
A linear French drain is a straightforward, inexpensive means to fix this kind of problem. In this particular scenario, it acts as a moat that protects your property by intercepting the groundwater rushing on the slope and directing it around and from your house’s foundation.
A linear French drain is a doable D.I.Y. project, should you don’t mind performing some backbreaking work (this does involve digging a trench, which in the end is actually a thing closely similar to a ditch) and you have the correct tools and materials (1″ round washed gravel, 4″ PVC pipe with drainage holes, a trenching spade or power trencher as well as a builder’s level)
So, let’s get down to the nitty-gritty both of how to develop a French drain, and how it works. To start with, you’ll need to dig an L-shaped or U-shaped trench system, 6″ wide and 24″ deep, four to six feet through the house. It’s important to not build the drain too nearby the house because, should you, you’ll be bringing water up against the cornerstone, which is exactly what you don’t want.
The key leg from the trench system needs to be dug up the slope from your house. To get a U-shaped French drain, it needs to be level and attached to two pipes on each side of the home with 90 degree PVC elbow joints. For the L-shaped drain, the main leg should slope down, at a pitch of a minimum of 1/8 inch per foot of fall, to the second leg that can run alongside the home, also connected by means of a 90 degree PVC elbow joint.
When you find yourself designing your drain system, you want to make gravity be right for you. Similar to a river, groundwater flows downhill, so you’ll have to work alongside natural slope of your residence and, if at all possible, hold the exit pipe come out above ground to give the groundwater a simple exit point.
Once you’ve decided on the layout of the system and done the heavy work of digging the trenches, it’s time to install the working elements of the drainage system: the gravel and pipes. First of all, 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 on top of this first layer of gravel, with all the holes pointing down, and after that complete the trench with increased gravel, to a single inch below ground level. Then all you want do is cover the trench with sod or sdxgas decorative touch of your own choosing. And you’re done. The next time there’s huge rain, excess ground water will enter your newly installed French drain and stay diverted around your home and discharged at the end of the exit pipe or pipes.
It’s commonly recommend that a French drain be lined with geotech fabric and 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 place to place it will be on the top of the trench to avoid silt and sediment from filtering down from above and filling in the air spaces involving the gravel. The majority of the water that enters a French drain is groundwater flowing sideways underground, not downwards from the surface. Groundwater is not really silty, it provides already had the silt and sediment filtered out of it since it trickled down through the topsoil. In the event you doubt this, just think about whether underground spring water and well water are clear or muddy. Both of them are of course usually crystal clear because soil is a natural water purifier.