French Drain Installation with not much “Fall” or Slope

Posted: May 24, 2020 in DIY French Drain, french drain, French Drain Information, French Drain Photos
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French Drain Installation can be tricky sometimes.  Recently we installed a French Drain in Norman with very little “Fall”.  This means that the “Intake” For the Drainage System is close to the same level as the “Exit.”  Simply Put, it is hard to make a Drain work if it isn’t ” Down Hill,” to where the water is going.

New French Drain

French Drain with very little fall

This was the Situation for the French Drain we installed last week in Norman.  The standing water was in the back yard.  There was only one direction that we could take the unwanted water to drain away.  In this case it was only slightly down hill.  The French Drain was installed at a shallow level in the back yard.  The solid drain pipe that was attached ran from the back yard, along the side of the house to a curb outlet at the street.

As the trench for the Drain Pipe was dug, it had to start shallow and slowly get slightly deeper as it approached the street.  This was an absolute Precision Job.  The trench could not be even an inch too deep or too shallow along its course.

At the street, a “Pop-Up” Emitter could not be used.  It would cause the water to stop flowing.  Two Install a Pop-up Emitter at the Exit of any Drainage System,  There must be at least 6 inches of “Fall” from the Drain to the Exit.

In Our Case, we only had 3 inches of fall to work with.

The solution was to Cut the curb and Install a Curb Outlet.

This process involves cutting the Curb with a concrete saw and placing a rectangular Curb outlet in the empty space.  We then put acrylic concrete around the outlet to make it look nice.

The fact that the outlet is square or rectangular is very important.

Many times I look at Round Curb outlets installed by my competitors and just shake my head!  This is a mistake.  Round Curb outlets are bad when the Drainage System is at Max Capacity and the pipe is completely full.  Air needs to be able to get into the pipe at the curb to ensure that the Drainage System can work at its Max.

The Drain will work with a Round Outlet, Just not very well.

Have you ever tried to Pour liquid out of a Jug or 2 liter bottle holding it completely upside down?

It Drains and Stops and Starts as the liquid comes out.  “It Chugs” and struggles to get air up inside the hole.  It doesn’t work very well.

A Square Outlet allows air to constantly flow into the top corners of the Curb Outlet.

As a result, Much more water is moved in the same size pipe.

new curb outlet

Curb outlet with more than 6 inches of fall

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