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I want to put a French drain at my patio and I am wondering how to connect the French drain in order for the water flow to go away.

Where and how should I finish the French drain?

At the moment my patio has a rodding eye (a "clean out") and I was wondering if it is possible to connect the French drain to the rodding eye.

However, since the rodding eye has only one output, I was thing to replace it with a bottle gully with two inputs--one that I will connect the French drain and the other one that goes to the sewage.

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As you can see, the red lines signifies where I will put the french drains, and I connect both of them. However, can I then connect them to rainwater drain? I am trying to find a way to finish the french drains in order for the water to flow away

Is this correct, or I need to do something else?

isherwood
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Dimitrios
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    In many areas you cannot connect a French drain (groundwater and/or stormwater drainage) to the sewage system at all. – Ecnerwal Nov 16 '22 at 13:38
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    I saw this and said, What's a 'rodding eye?' Apparently it's an "access port for inspecting and cleaning a storm water drain" https://drainfast.co.uk/blog/should-rodding-eyes-be-sealed/#:~:text=What%20is%20a%20rodding%20eye,surface%20water%20(stormwater)%20drain. – Triplefault Nov 16 '22 at 13:39
  • A picture or diagram of your yard would help. Indicate where slopes run and give an indication of how steeply it's sloped. Usually, a French drain would exit to daylight at a low point in the yard where the water can continue to flow off the property. – FreeMan Nov 16 '22 at 13:47
  • @Triplefault good sleuthing, thanks! In America we'd call that a "clean out". – FreeMan Nov 16 '22 at 13:47
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    Where do your roof gutters drain to? It's very likely not sewage but storm drain, rock pit, waterway etc... And that rodding eye (clean out), is that for storm or sewage? – P2000 Nov 16 '22 at 14:40

2 Answers2

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On a rainy day, confirm that the rodding eye is for your storm drain: open it up and see if it has rain water flowing.

If you can't wait for rain, run water form a garden hose into the rain pipe; if it appears dry, take your time and try different rain pipes.

This is an important step. Do not make assumptions. In many jurisdictions it is prohibited and inadvisable to empty rain/storm water into the sanitary system. Also, a sanitary system will require a P trap, which a storm drain does not & will not have.

If that's indeed a storm drain clean out, you can have your french drain empty into the drain pipe at that rodding eye. Dig to the depth of the storm drain pipe there, which should be below the depth of the french drain drain-pipe, and connect the two with a T or Wye.

If it is not a clean out for the storm drain pipe, you can dig at the base of the rain pipe and determine a suitable spot to make a connection to the pipe system you find there.

Ideally you would follow the existing drain pipe to its lowest point, perhaps near a corner of the french drain system, and make a connection there, with a new clean out, but this is not necessary.

This allows you to lay the new drain system's pipe a bit lower or give it more slope. Whether it's feasible also depends on which way the storm drain is headed, and whether you'd rather not want to add another clean out for aesthetic reasons.

P2000
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You need to answer the following questions.

  1. The existing "rodding eye" is a cleanout for a pipe that carries water from A to B. Where is A, and where is B?
  2. What is the capacity of the pipe and what is the amount of water currently transported by the pipe during heavy rainfall?
  3. Does "A" already include groundwater from your entire back yard? If not, what is the amount of water that will be collected by your french drains during a heavy storm? Where does that water curently floow? Will you exceed the capacity of the pipe if you divert all this new water through the pipe?

You get the general idea?

Maybe your roof water goes to the storm drain via the pipe (with the rodding eye) and your ground water rolls into the street and your neighbors' yards. Maybe your ground water eventually ends up in the same storm drain, maybe not. Maybe it can't get there through the existing pipe, maybe it can, maybe it already does.

Can you answer all these questions?

You have to think big picture ... where does ALL the water come from and where does ALL of it go to .... you can't just dig a trench and connect it to something the way you would plug a lamp into the wall.

jay613
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