Perforated Pipe
When and How To Use French Drains in the Landscape

Sometimes it is advisable to use perforated pipe as a drainage solution. This is also known as a french drain. Perforated drainage pipe is often used as an alternative to re-grading properties. It is a relatively easy way to correct drainage issues and it is not that expensive. there are some different types and also different ways to connect them to lead the water away.

Perforated Drainage Pipe

There are various types of perforated plastic drainage pipe.

Plastic Drainage Pipe

This is a pvc drainage pipe that has holes in the top. Water enters from up above and enters the pipe through the holes. This type of drainage pipe is not flexible, but very stiff.

Corrugated Drainage Pipe

This type of pipe is black with slits all around the pipe. The pipe is flexible. The concept here is that water will enter through the top, but if water saturates the ground it can enter from beneath the pipe also. I had this type installed on my own property at my house foundation and it is working very well.

Installing Drainage Pipe

The plastic drainage pipe will be set into a trench. French drains (another name for them) are typically covered with filter fabric so that dirt does not enter the pipes. A layer of stone is placed on top of the piping for better percolation down to the pipe. The depth of the trench should allow for the width of the pipe along with a layer of stone on top.

The pipe must be pitched in the direction that you want to direct the water. I like to use 1/4" per foot. Technically, you can pitch it less since a smooth pvc drainage pipe has little friction. I like to over compensate slightly to be safe.

The perforated pipe is connected to an underground pvc drainage pipe where the water continues to flow. The solid pipe is also pitched and should be at least or greater than the pitch of the perforated pipe. The water in the solid pipe can exit in a few different ways.

The solid pipe can exit into a lawn drain. An additional pipe connected to the lawn drain can lead the water to another area off your property, such as a water collection system at the road. Check with your municipality regarding this as some allow it while others do not.
The solid pipe can lead to another area on your property such as an unused lawn area or woods. The opening of the pipe would exit at ground level so you need to have sufficient sloe on your property to do this.
It can also be led directly to a sewer at the road, but once again, check with your town to see if this is legal where you live.

Which way you choose will depend on your own property.

Plastic drainage pipe is often used near the house foundation if the ground slopes towards the house and you do not want to re-grade your property (as was my own situation). It can also be used in other areas. For example, you might choose this type of landscape drain if the land slopes towards your patio and there is nowhere else to channel the water. The pipe would be installed at the patio edge beneath the ground. You can cover it with decorative stone.

There are other drainage solutions for yards too, such as swales, trench drains, re-grading, or combinations of these methods.

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Perforated Pipe
When and How To Use French Drains in the Landscape