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Patio Channel Drainage Query

Discussion in 'In the Garden' started by Happyunited, 12 Mar 2021.

  1. Happyunited

    Happyunited

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    Hello,

    After completing an extension last year my next project is to start the patio at the rear of the property. There is already 150mm type 1 MOT in the area (needs compacting). I've had 3 quotes for the same thing (probably honed Indian stone) and all 3 have said channel drain along the house to the existing gully trap as shown in the picture. I've dug the trench for the drain and a trench for some wooden sleepers that will be used to separate the patio from the lawn. This will have a slight step up to the lawn, approx. 50mm.

    Having spoken to some drainage engineers and reading various forums/blogs there seems mixed views in sloping the patio TOWARDS the property. Note that the top of the aco drain will be 150mm below DPC (in line with the trench block in the image). Did the 3 quotes say channel drain along the house simply because of where the gully trap is thus making it easier to connect to? Am I creating a problem that doesn't exist here by directing water towards the house?

    Drainage calcs for patio area state the channel will be 83% full for 1:100 year event.

    Any advice is greatly appreciated.

    https://ibb.co/4gqwjV3
     
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  3. Celeronmanuk

    Celeronmanuk

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    I'd always try and direct water away from the house where possible. What does the outlet of the bottle gulley connect into?

    BTW, does the stone manufacturer specify 1:60 or can you use 1:80? It's a bit less noticeable.
     
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  4. Happyunited

    Happyunited

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    Outlet of the gulley connects to a combined manhole about 750mm away so in terms of amending existing drainage the work is minimal. Obviously running the channel at 3m offset from the house will leave more work with drainage back to the trap.

    1:60 seems to be the norm.

    Regarding the aco hex and them joining together, they click at the bottom but are a bit loose at the top. Obviously, these sit in concrete but they don't seem watertight, is there something I'm missing or is there a degree of water escape expecting? or silicone the joints/end caps?

    Thanks
     
  5. Celeronmanuk

    Celeronmanuk

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  7. Happyunited

    Happyunited

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    Have you got any pictures?
     
  8. Happyunited

    Happyunited

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    Anyone got any more advice on this please?
     
  9. Ian H

    Ian H

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    As long as the water actually goes into the ACO I would have it anywhere.
     
  10. Celeronmanuk

    Celeronmanuk

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    Not that really shows the fall.

    [​IMG]

    The channel drain is just in front of the steps. Flows into a silt trap (under the sofa) and then to a 2m3 crate soak away under the lawn.
     
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