Knowledgebase

French Drain for Overworked Rain Garden #906971

Asked June 23, 2025, 6:11 PM EDT

What information might you have that would help me plan a French drain? Do you have a list of contractors that install these? Thanks

Ramsey County Minnesota

Expert Response

The trench for a French drain should be approximately 12 to 18 inches wide and 18 to 24 inches deep. This sizing helps ensure adequate water flow and easy maintenance.
https://www.lsuagcenter.com/articles/page<personal data hidden>13

https://ask.extension.org/kb/faq.php?id=551198

You'll typically need a perforated pipe, usually around 4 inches in diameter, which should be laid into the trench's base and covered with washed gravel (typically 1 inch in size). This setup allows for proper drainage while preventing clogging.
It's beneficial to line the trench with geotextile fabric. This fabric prevents soil from mixing with the gravel, which could reduce drainage efficiency.  Make sure to site the drain in areas where water collects and ensure that the trench has a slight slope to help direct water away from your rain garden and towards a suitable outlet.
When planning where the water will drain, consider using a pop-up drainage system to distribute the water more widely, if preferred.
The UMN cannot recommend specific contractors.

Linda G Tenneson, Benton County Extension Master Gardener & Tree Care Advisor Replied June 23, 2025, 9:48 PM EDT

Thank you!

 

From: ask=<personal data hidden> On Behalf Of Ask Extension
Sent: Monday, June 23, 2025 8:49 PM
To: Mark Nichols
Subject: Re: French Drain for Overworked Rain Garden (#0176887)

 

The Question Asker Replied July 10, 2025, 3:05 PM EDT

Loading ...