can downspout drainline be tied to french drain perf. pipe?

[Chitra Paul]

I need a french drain in my backyard,which slopes toward my house. I also discovered that the builder plumbed my 2 rear downspouts AND a yard drain into my footer drain/sump. An “expert” gave me an estimate to install a french drain and suggests he tie the downspouts into the perforated french drain pipe, but I prefer installing a seperate, unperforated drainline above the frenchdrain perf. pipe in the same trench. Who is right? Thanks!!!

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[nicktheplumberParticipant]

The purpose of a perforated perimeter drain around a foundation is to drain water that soaks into the ground. These drains are placed at the level of the footing and they divert the water away from the footing. They must be embedded in gravel.

You should NOT run roof downspouts into these drains. These drains are meant to handle water that percolates through the soil from the surface. Running downspouts into the perforated perimeter drain will overload the drain, unless it is hugely overdesigned. The downspounts from the roof should be run into individual pipes or splashblocks that carry the water to a graded surface more than 6 feet from the foundation, OR these downspouts may be run into a solid drainpipe buried above the perimeter drain, and this solid drain pipe should carry the water well away from the house. say into a dry well, onto the street, or into the municipal sewer.

NtP

[wilbur27Participant]

I understand the purpose of the footer drain AND that the downspouts should not be tied into the footer drain. I need a french drain in my backyard and I need to re route the two downspouts and the yard drain that the builder did route into my footer drain. My question is: can the 2 downspouts be tied into the proposed french drain perf pipe or should the downspouts have their own,solid pipe? Can the new downspout line be put in the same, gravel filled trench as the new perf pipe for the french drain but above the perf pipe? The “expert” that gave me an estimate for the french drain claims I can route the 2 downspouts into the new french drain perf pipe and that I dont need a second,dedicated line for the downspouts. Also, he thinks wrapping the french perf pipe with a sock is a waste of time, but that seems to make sense to me. Thanks a million!!

[nicktheplumberParticipant]

I thought I answered your question in a politic way…but perhaps I should be more direct.

If your “expert” said it was ok to run the downspouts into the perforated footing drain, he was, in my opinion, mistaken. For the reasons I said.

You can (and should) run the downspouts into a solid line above the French drain. Sure, you can embed that solid line in the same gravel that houses your footing drain. What difference does it make, since the solid line will not leach water into the perforated drain?

I have to admit that I am not an expert in soil drainage. My work as a plumber includes a lot of sewer work, but your application is not really sewer work.

NtP

[Phil_HParticipant]

Got to love the English language. Some people use the term “French Drain” to describe a disposal field and some people use the term to describe a system to collect water. They kinda look the same, but it depends which way the water is flowing. So Wilbur, it depends on how the system is designed and where is the so called french drain.
Phil

[wilbur27Participant]

What the “expert” is proposing for the french drain is a new, gravel filled collection trench about 14 to 20″ deep, sloped downhill, with a 4″perf pipe in the bottom. The output of this french drain would tie into my existing 4″ solid lines that run to the street storm sewer. This new perf. pipe would not be in the same “trench” as my footer drain, which obviously is about 1 story under the ground, but in a new, shallow trench near the surface. This gravel filled trench would then be covered back over with a thin layer of topsoil and grass. Also, the expert recommends tying my downspouts into this new 4″ perf pipe. I cant understand why the water volume from the downspouts wont interfere with the water flowing from the gravel trench into the perf. pipe. Why doesnt the water leak out of the holes in the perf pipe into the gravel, like a long,expensive,undergound sprinkler? Also, the expert says wrapping the perf pipe with a filter sock is not needed, because the gravel above acts like a filter. He says the perf. pipe would lie directly up against the clay “bottom” of the trench, with some of the holes blocked. Most of what I have read suggests digging the downward sloping trench, putting in a couple inches of gravel, then the sock wrapped perf. pipe,then more gravel,then a little topsoil and grass. An alternative is to line the trench with landscaping fabric as a filter,then 2″ of gravel, then perf. pipe,then gravel. Wrap the landscape fabric over the top gravel to close the filterdd soil and grass. My thought was,dig the trenchdd 2″ of gravel,install the sock wrapped 4″ perf. pipe, then a solid 4″ pipe for the downspouts AND to add surface drain grids later if they are needed in low areas,top with gravel and soil. Pipe is cheap,easier to carry than gravel, and I dont feel like digging the perf. pipe up if this scheme does not work. I am infamous for making things more complicated than they have to be, but….. Your thoughts? Wilbur

[nicktheplumberParticipant]

I cant understand why the water volume from the downspouts wont interfere with the water flowing from the gravel trench into the perf. pipe. Why doesnt the water leak out of the holes in the perf pipe into the gravel, like a long,expensive,undergound sprinkler?
…
Also, the expert says wrapping the perf pipe with a filter sock is not needed, because the gravel above acts like a filter. He says the perf. pipe would lie directly up against the clay “bottom” of the trench, with some of the holes blocked…
but….. Your thoughts? Wilbur [/QUOTE]

Wilbur,

I think we’ve beaten this dead horse enough, and she ain’t coming back to life… Your comments above indicate you have your doubts about your contractor’s advice. As I’ve explained in two earlier responses, I also have doubts. Your first comment about the downspouts overloading the perf pipe drainage field is absolutely 100% correct.

Re: about the recommendation of laying the perf pipe directly on an impermeable bed (clay), that is rediculous! You need to lay the perf-drain pipe over a bed of gravel and pourous soil so that the water leaches harmlessly from the foundation. I did say that I’m not an expert on soil drainage, but I keep informed about the other building trades, and it is my understanding that the purpose of foundation drains is to divert water away from foundations. While it MAY be possible to do so by running a perimeter perf drain in direct contact with clay soil (in which case you hope that the perf drain collects soil H2O from above and carries it safely away). But if that is your intention, why use the pipe at all? Just make a trench into the clay around the foundation, fill it with gravel, and cover with topsoil and be sure that the gravel trench runs away from the house…

And as regards pouring roof runoff (which is considerable in a downpour) into a perforated pipe around your foundation, that is quite simply madness.

I may be totally wrong about all this, and if I am I am sure my colleagues here will let me know.

BTW, why don’t you get a second opinion from another contractor in your area, or ask your local building inspector for an opinion?

NtP

[wilbur27Participant]

ntp: thanks a lot for for all your thoughts and advise. I think you have nudged me to follow what seems reason-able and go with the 2 pipe system. In my area (northern Ohio) it is hard enough to find a contractor that will keep an appointment, let alone getting a second opinion. The building inspector in my town is the same idiot that approved the builder tying the downspouts into the footer drain, and he has avoided responding to 8 calls/visits concerning my neighbors commercial property draining into my backyard, which has compounded my need for a french drain. I gave up trying to deal with him, jumped the fence, added a 6″ liner to my neighbors gutter,reattached his downspouts and ran a 100′ of cheap corrogated pipe to bypass his non functional underground line. His building was being undermined by the action of the runoff in 2 places. Sometimes, action is more satisfying than @*($%# from policitians. I think I will call the expert tomorrow and tell him I have decided to do the work myself. My back will be sorry, but I will feel a little bit more satisfaction. I know a couple young,strong backs I can hire . Wilbur

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