French drains which, despite their name, originated in the United States, essentially work by providing invasive groundwater with a path of least resistance by means of 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 Especially with Tiles.
Nowadays, French drains are typically utilized to combat flooding problems due to surface or groundwater that the property owner may be having, especially affecting their lawn, foundation or basement. Also, they are sometimes used to drain off liquid effluent from septic tanks.
The fundamental design, a gravel-filled trench, is straightforward however for it to carry on working on the long run, it’s essential that it be executed.
Flooding problems are usually associated with sloping ground, non-porous clayey soil, or a combination of the 2. For instance, if your property is built over a slope together with your neighbors’ house occupying a great deal higher up the slope, heavy rainfall can precipitate an accumulation of groundwater rushing down off their property and on to your own. In case your soil is struggling to absorb all that water, you could very well experience damage to your house’s foundation, or leakage right into a crawlspace or basement underneath the ground floor of the house.
A linear French drain is a straightforward, inexpensive answer to this type of problem. Within this scenario, it acts as a moat that protects your house by intercepting the groundwater rushing down the slope and directing it around and out of your house’s foundation.
A linear French drain is a doable D.I.Y. project, in the event you don’t mind performing some backbreaking work (this may involve digging a trench, which after all is a thing closely similar to a ditch) and you will have the correct 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 down to the nitty-gritty both how to build a French drain, and how it operates. To begin with, you’ll have to dig an L-shaped or U-shaped trench system, 6″ wide and 24″ deep, 4-6 feet from your house. It’s important never to build the drain too nearby the house because, should you do, you’ll be bringing water up against the cornerstone, which is precisely what you don’t want.
The key leg of the trench system should be dug the slope from your house. For a U-shaped French drain, it needs to be level and attached to two pipes on both sides of your home with 90 degree PVC elbow joints. To have an L-shaped drain, the key leg should slope down, with a pitch of at least 1/8 inch per foot of fall, for the second leg that will run alongside your house, also connected through a 90 degree PVC elbow joint.
When you find yourself designing your drain system, you need to make gravity meet your needs. Just like a river, groundwater flows downhill, so you’ll have to work with the natural slope of your home and, if possible, have the exit pipe appear 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 parts of the drainage system: the gravel and pipes. To begin with, tamp down any loose soil towards 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 the holes pointing down, then complete the trench with additional gravel, to 1 inch below ground level. Then all you need to do is cover the trench with sod or sdxgas decorative touch of your personal choosing. And you’re done. The next time there’s a huge rain, excess ground water will enter your newly installed French drain and become diverted around your property and discharged after 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 likely to use geotech fabric anywhere, the spot to place it will be on the top of the trench to stop silt and sediment from filtering down from above and filling inside the air spaces in between the gravel. A lot of the water that enters a French drain is groundwater flowing sideways underground, not downwards through the surface. Groundwater will not be silty, it provides already had the silt and sediment filtered out of it because it trickled down with the topsoil. If you doubt this, just ask yourself whether underground spring water and well water are clear or muddy. Each of them are needless to say usually magnificent because soil is a natural water purifier.