How to Install a Dry Well and Divert Rain Run-Off

In this video, This Old House landscape contractor Roger Cook controls rain run-off.

Placement Note: When choosing your dry-well location, position it at least 10 feet from the foundation and at least 3 feet from any property line. Dig the hole about 4 feet deep and wide, and line it with landscape fabric cut from a 6-foot-long roll to prevent soil from clogging the stones around the dry well. Leave enough fabric outside the hole so that you can cover the stones once the dry well is installed.

Steps:

1. Lay out lengths of 4-inch-diameter PVC pipe from the end of the downspout out to the dry-well location. Start with two 10-foot lengths of standard pipe, then lay out two 10-foot lengths of perforated pipe.

Pro Tip: Roger, This Old House plumbing and heating expert, recommends using plastic dry well chambers instead of traditional concrete ones to save on labor costs: “They’re heavy and hard to maneuver, and in a small site like this, hard to get in place, so that’s why we’re going to use these plastic chambers. This can easily be lifted by two guys and set in place.” The lighter materials can significantly reduce the time and effort — and potentially the number of hands — needed on the job.

2. Dig along each side of the standard pipe. Cut into the soil about 2 inches from either side of the pipe.

3. Upon reaching the perforated pipe dig into the soil about 6 inches from either side of the pipe.

4. Move the pipes aside and dig a 6- to 8-inch-deep trench.

5. Set the standard pipes into the trench and use a 4-foot level to ensure they pitch about ¼ inch per foot toward the dry well.

6. Line the remainder of the trench with landscape fabric, then cover the fabric with about 2 inches of stone.

7. Set the perforated pipe on top of the stone, add more stone, then wrap the landscape fabric around the pipe.

8. Connect the standard PVC pipe to the end of the downspout with a PVC 90 degree elbow and downspout adapter fitting.

9. Backfill around all pipes with soil dug from the trenches.

10. At the end of the perforated pipe, dig a hole for the dry well that’s approximately three times wider and deeper than the dry well.

11. Line the dry-well hole with landscape fabric, then pour 4 to 6 inches of stone into the bottom of the hole. Spread the stone level.

12. Place the dry well in the hole, making sure the end of the perforated pipe extends into the dry well.

13. Backfill around the dry well with stone.

14. Set the plastic cover onto the dry well and tap it down with a rubber mallet.

15. Install a pop-up valve into the dry-well cover.

16. Cover the dry well with soil, making sure you don’t bury the pop-up valve.

17. Rake the area over the dry well level, then plant grass seed.

Pro Tip: Roger, This Old House landscape contractor, explains the reasoning behind the two pipe types: “The solid pipe ensures that we’re going to get the water away from the house. Then this is going to allow me to start leaching water down into the ground. It’s going to be a seepage trench. So even before we get to the dry well, we’re already getting water down into the ground.”

Maintenance Tip: When a buried downspout backs up, a clogged dry well could be the cause. Dry wells with a hatch in the top can be cleaned out through the access point. Otherwise, the entire dry well may need to be excavated — so choosing a dry well with a removable cover, like the pop-up valve described above, makes long-term maintenance much easier.