French drains which, despite their name, originated in america, essentially work by offering invasive groundwater with a path of least resistance by way of 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 typically employed to combat flooding problems due to surface or groundwater that the home owner might be having, especially affecting their lawn, foundation or basement. Also, they are sometimes utilized to drain off liquid effluent from septic tanks.
The essential design, a gravel-filled trench, is straightforward but for it to continue working on the long term, it’s important that it be well executed.
Flooding troubles are usually related to sloping ground, non-porous clayey soil, or a mixture of both. For instance, in case your property is built over a slope along with your neighbors’ house occupying a whole lot higher up the slope, heavy rainfall can precipitate an accumulation of groundwater rushing down using their property and on your own. If your soil is unable to absorb all that water, you could very well experience injury to your house’s foundation, or leakage right into a crawlspace or basement beneath the ground floor of the house.
A linear French drain is a straightforward, cost-effective means to fix such a problem. Within this scenario, it works as a moat that protects your property by intercepting the groundwater rushing along the slope and directing it around and out of your house’s foundation.
A linear French drain is a doable D.I.Y. project, if you don’t mind performing some backbreaking work (this may involve digging a trench, which all things considered is really 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 right down to the nitty-gritty each of how to build a French drain, and the way it works. First of all, you’ll have to dig an L-shaped or U-shaped trench system, 6″ wide and 24″ deep, 4-6 feet through the house. It’s important never to build the drain too near the house because, if you do, you’ll be bringing water up against the foundation, which is exactly what you don’t want.
The main leg of the trench system ought to be dug in the slope through the house. For a U-shaped French drain, it ought to be level and connected to two pipes on each side of the home with 90 degree PVC elbow joints. For an L-shaped drain, the main leg should slope down, with a pitch of at the very least 1/8 inch per foot of fall, towards the second leg which will run alongside the home, also connected by means of a 90 degree PVC elbow joint.
When you are designing your drain system, you need to make gravity be right for you. Just like a river, groundwater flows downhill, so you’ll have to work with natural slope of your property and, if possible, have the exit pipe come out above ground to provide the groundwater an 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 for you to install the working parts of the drainage system: the gravel and pipes. First of all, tamp down any loose soil in the bottom of the trench and line it with 1 to 2 inches of gravel, lay the PVC pipes on the top of this primary layer of gravel, using the holes pointing down, then fill in the trench with additional 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 choosing. And you’re done. The very next time there’s a heavy rain, excess ground water will enter your newly installed French drain and be diverted around your property and discharged at the end of the exit pipe or pipes.
It’s commonly advise that a French drain be lined with geotech fabric and also the piping be wrapped in a geotech sock to avoid it from becoming clogged with silt. I don’t recommend doing either. Should you be likely to use geotech fabric anywhere, the area to put it might be along with the trench to avoid silt and sediment from filtering down from above and filling within the air spaces involving 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 has already had the silt and sediment filtered out of it since it trickled down from the topsoil. In the event you doubt this, just consider whether underground spring water and well water are clear or muddy. Both of them are of course usually really clear because soil is a natural water purifier.