A pipeless French drain doesn't have a pipe and has more internal resistance to the flow of water. Therefore, it can't evacuate as much surface water.
By definition french drains do not require pipe. They are just artificial trenches using buried rock or gravel to direct water to another area. Although building a french drain without a perforated pipe is pretty stupid.
Line the Trench with Filter Fabric
To keep the French drain free of dirt, silt and tree roots, lay water-permeable filter fabric or a weed barrier over the gravel bedding in the trench. Leave the filter fabric open with at least 10 inches of excess fabric at the sides.
French Drain Pipe Characteristics
Regardless of what the pipe is made of, it must be slotted or perforated at regular intervals to allow water to enter and flow through the system.
But which gravel is ideal for a French drain? Hard rocks like washed river rock or granite chips are the ideal gravel for French drains. The gravel pieces should ideally average at least 1′′ wide to provide the best permeability for water to run along.
It's connected to pipes to guide water away from your home. The first part of French drains is the elevated or higher end, referred to as a drain field. The drain field is where the groundwater or excess surface water enters the drainpipes.
Clay soil has poor permeability, meaning it doesn't allow water to pass through easily. In such cases, the effectiveness of a French drain may be limited as the water may struggle to drain away from the area efficiently. French drains may not be suitable for areas with high water tables.
Permits Needed to Install a French Drain
Generally, a small French drain on your property that doesn't change the flow of runoff entering and exiting your yard won't need a permit. Major projects that warrant your French drain to discharge into a municipal sewer or roadside ditch, however, do require one.
Clogging and Blockages
Clogging is one of the leading causes of French drain failure, often due to root intrusion or sediment build-up.
8 cons of French drains
May require regular maintenance. Care must be taken not to hit utility lines when digging for installation. Installing them may involve digging up your yard or even pavement. If the pipe gets clogged, it can be difficult to find and fix the problem area on your own.
Use Natural 1-1/2" round rock for best drainage. Washed rock is ideal. Avoid small pea gravel as the spaces in between stone is smaller minimizing flow rates. Avoid Crushed Rock (minus) that compacts and has "fines" that will clog pipe inlets.
Yes, you should wrap the French drain's gravel-filled trench with a permeable filter fabric. This fabric helps to prevent soil and debris from clogging the drain while still allowing water to enter the system.
While corrugated pipes have their place in some applications, PVC is the sound solution for a French pipe installation. At Align Foundation Repair, this is our go-to material for underground drainage systems.
French drains use gravity to move water away from the home and down through a pipe to an exit point. Exit points include the street, a grassy area with heavy sun exposure, or an existing underground drainage system.
It is not absolutely necessary to use perforated pipe to create a French Drain. However keep in mind if you remove the Perforated Pipe the water flow will be slower through the French Drain. If you do not use a Perforated Pipe consider increasing the size of the stone to 1 1/2”.
You'll likely need a permit since this project may require soil grading to avoid drainage issues. Repairing your floor may be more cost-efficient than replacing it if grading is necessary. No permit may be required to hang drywall on exposed wooden wall studs in your garage.
8-10” deep is good for a French drain. I suggest using a filter fabric to cover the pipe with holes. This will keep dirt from going into the pipe and clogging it up. As long as the the ditch and drainage pipe have fall (not under 1/8 inch per foot) then you should be good.
Gravel trenches can be adapted to suit various drainage needs, from small garden beds to larger yard areas. They are less expensive to install than traditional French drains, and you can DIY a gravel trench with some essential tools and materials.
French drains are best suited for properties with moderate to severe water drainage issues, particularly in areas with heavy rain or poor soil drainage.
What landscaping projects does gravel help with drainage the best? Gravel does help with drainage for most landscaping projects. But it all depends on the type of gravel used and the drainage project. For most projects, gravel with a size of 1/2 inch to 1 inch will suffice.
Although French drains are low-maintenance, they are not entirely free of potential issues. Over time, the system can become clogged with silt, roots, or debris. When this happens, water may pool again in areas the drain was meant to protect. Regular inspections can help identify problems early before they escalate.
A French drain needs to be surrounded by gravel in order to filter out silt and prevent clogging the drain pipe.
The optimally installed French drain does not necessarily need an end point. Ideally, as the excess water from one area runs down the drain, it will be distributed more evenly across your yard and absorbed.