5 Common French Drain Mistakes

1. Utilizing the wrong kind of drainage rock

Proper drainage rock is crucial for adequate permeability and drainage when constructing a French drain system. Using a clean natural round stone for your drain fill material enables good water flow through the aggregate and to the piping, and won’t clog the system.

When available the recommended choice of stone is 1″ Clean Rock.

  • Use Natural 1″ washed rock for best drainage results.
  • Avoid any smaller pea gravel, as the spaces in between stone is smaller creating a minimizing flow rate.
  • Avoid any type of Crushed Rock that compacts and has “fines” that will clog pipe inlets.

2. Not lining the trench & pipe with drain fabric

Another issue contributing to early French drain failure is not lining the trench with a non-woven geotextile drainage fabric as recommended. The drainage fabric acts as a soil separator and prevents dirt and debris from mixing with your rock fill while allowing the water to freely flow to the pipe and to the outlets.

By not installing this drainage fabric, there is nothing stopping sediment from mixing in with your drain rock. This type of contamination will lead to reduced capacity of the system, and ultimately clogging/failure of your French Drain over time.

If you want to ensure your system continually performs correctly for years to come, then be sure to line your trench with the correct drainage fabric using the Wrap installation method.

  • High quality drainage fabric can last for decades without issue.
  • Avoid using socked wrapped perforated pipe by itself without drainage fabric as it tends to easily clog with dirt/soil.

3. Placing the excavated soil back into the trench

Trenching can be a chore and sometimes contractors and home owners find it easier to put the additional excavated soil/clay on top of the newly created drain system. Adding soil back into the trench should be avoided, unless you are putting a sod strip on the drain to make it blend into the surround yard. If so, you should only use a thin layer of dirt.

4. Lack of positive slope for the drainage system may cause problems

The pooling of water in a drain pipe can lead to some major issues and may create problems for your French Drain – drainage system. It’s important that you take the time to ensure the pipe is at an angle that will allow the water to drain out by the use of gravity. Affordable drainage of North Houston always keeps this in mind when installing any of our drainage systems.

Slope Discussion:

No Slope: When the pipe is completely flat, water requires more energy to move through the drain. Zero slope systems will not allow sub-surface water to drain properly.

Low Spots: Be mindful to avoid low spots or dips in your French drain trench. Pooling can occur, increasing the retained water within the drainage line, and hindering the water flow. This kind of pooling can be extremely problematic as it attracts one of the most detrimental things to drains which are tree roots. Tree roots naturally seek out moisture in order to promote growth and are attracted to the standing water in your yard or new drain. Once roots enter the system they will block flow and reduce the effectiveness of the drainage system. Our French Drain Contractors are very mindful of this when installing your drain project in Spring, Texas – Conroe, Texas – Magnolia, Texas – Tomball, Texas – or the surrounding areas of North Houston.

A properly built French drain that has low spots and retains water will not really stop tree roots. These roots can, and will, gradually grow through the fabric destroying the integrity of your system as they seek moisture and room to grow. It is important that all of the water is able to dissipate, avoiding the invasion of these tree root systems.

Negative Slope: A less common but still undesirable pipe position is when the property and/or pipe has a negative grade. This condition makes it impossible for water to flow through the pipe freely using gravity. The water table in the ground has to rise to a high enough level of saturation in order for it to flow through the system, which is not ideal. Negative slope in your drainage pipe is bad if the goal is to drain away from a building as the negative slope can draw water back towards a structure or foundation, making things worse. In these cases, a pump drainage system may be in order.

Good Slope: Greater than 1.5% grade slope is ideal for your trench. This will allow water to drain away from the inlet and ensure gravity does all the work to distribute it along your drain lines or through the outlet.

5. Gravel-Only drain installation without a Drain-pipe

A common mistake made by homeowners intending on installing drainage is leaving out the drain pipe, which sometimes turns into a big problem. By missing this important step, the drain cannot handle heavy water flow, which reduces its effectiveness at removing idle water. The purpose of a drain is to direct pooling surface and subsurface water where you need it to go so the area becomes less of a problem.

Having a drain pipe, most commonly a 4″ perforated pipe surrounded by round drain rock and the proper fabric provides the capacity to move this water away from structures and prevent pooling.


The bottom line is to always have a professional yard drainage & French Drain Contractor install all of your drainage systems. Affordable drainage of North Houston services Conroe, Texas – Magnolia, Texas – Spring, Texas – Tomball, Texas – The Woodlands, Texas as well as the surrounding areas. We offer free drainage estimates for your convenience.

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