Do not vent hand excavated french drains into rain drain discharges
A common mistake that I encounter often when inspecting for home drainage problems, is the practice of homeowners, contractors, or would be contractors, installing french drains and making a real mess of it. A common error involves the installation of a french drain that vents into the rain drain discharge on the side of the home.
The perforated pipe in the french drain, which may or may not be hand excavated, vents at the foundation where the rain drain discharge is located. This is not recommended. A homeowner called me yesterday with the same story. Her relative had told her that he understood home drainage and the installation of french drains, and that for $1000. he would solve her groundwater in the crawlspace problem. The reality however following the home drainage installation is that the effort of this “would be” french drain installer created more groundwater in the crawlspace than there was before the work was done.
The person attempting to install the french drain did a rough ditch with no slope, and then placed a perforated pipe in the bottom of it. He then tried to connect it to the abs solid pipe that is the rain drain discharge. As I said before, this is not recommended, and does more damage than good.
Perforated pipe sloped to the foundation area leaches out the groundwater next to the foundation. The groundwater spills out of the perforated pipe on the foundation wall before it can be collected by the rain drain discharge. In addition to poor engineering, the silt from the poorly excavated french drain will likely clog the rain drain discharge in time, causing the downspout to overflow at the foundation area where the downspout is plumbed to the rain drain discharge. The plugging of the rain drain discharges will put more roof water into the crawlspace or basement, and place further monetary requirements on the homeowner to solve the problem.
I see some of the most blatant rip off tactics used to bilk homeowners out of their hard earned cash with respect to home groundwater removal and home drainage. It is advised that you study and learn before you become a victim of bad home drainage science. If you read this web site, whether or not you intend to employ a home drainage contractor or do it yourself, you will be years ahead in knowledge of home drainage and spot these flim flam home drainage guys a mile away.
The example above of trying to connect a french drain to a rain drain discharge is only one of the many bad home drainage science scams that are perpetrated on homeowners everywhere.
The Portland, Oregon area is a mature home drainage market with respect to home drainage knowledge, but even here the bad science creeps in and causes homeowners major monetary and functional problems with respect to their home groundwater removal problems.