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Soakaway Build

g333g333 Posts: 125
in Problem solving
Hi

Looking for best way to build a soakaway, read a few different ways online so anyone with knowledge on this would be great to hear what worked best.

The soakaway will be 1x1x1m is this big enough?
Should I line the hole with a Geotextile fabic if so is the the sides only or bottom also?
Should I use creates?
What should be the backfill contain? 5-10mm gravel, then 10-20mm gravel, topsoil and bark?

Thanks

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Posts

  • nick615nick615 Posts: 1,487
    g333  I presume we're talking about the same thing but this may help.  I made a couple some years back to cope with dispersing water from a downpipe.  I dug a pit, about a metre wide x 1.5 long x 1.5 deep.  I filled the pit with the largest stones I could find from a 'house brick' upwards, some equivalent to 6-8 times that size, up to the level where the water came in.  Across the top I laid several layers of woven plastic coal sacks to prevent soil washing down into it.  I completed the exercise by covering with loose soil and haven't had any problems since.
  • TheVanguardTheVanguard Posts: 136
    We had one replaced last year...the basic process was...

    Dig a big hole

    Test it by pouring loads of water in it to make sure it drains away...

    Then put in a plastic crate wrapped in fabric, and connect up to the pipe. 

    Then refilled.


    I also then made a huge mistake...I assumed it would be a bit damp in the area and a great place to plant some hydrangeas on top as they are quite shallow rooted..of course it’s the opposite and it’s bone dry and I spent most of last year pouring water on them and in an effort to keep them alive. 
  • g333g333 Posts: 125
    Did you pour fine gravel over the create before wrapping in fabrix?
  • g333g333 Posts: 125
    edited March 2021
    Any other suggestions on this? Is soakaway crate best option?

    If using crates do the get backfilled with fine gravel before wrapping in fabric?

    Is one layer of crate enough for 1m deep?

    If not using a crate the what’s best the layers I suggested below or broken up bricks?

    5-10mm gravel 
    10-20 mm gravel
    topsoil
    bark


  • wild edgeswild edges Posts: 10,497
    Well how much water do you need to deal with? To answer any of your questions we'd need to know that plus the results of a percolation test and how much ground you have to deal with (that's at least 5m away from any structures and roads). How much water goes in and how quickly, how quicky can the water drain away? That's the bones of soakaway design. Rubble pits only work if the soil drains well and you have a low volume of water. 
    If you can keep your head, while those around you are losing theirs, you may not have grasped the seriousness of the situation.
  • g333g333 Posts: 125
    edited March 2021
    I have a side border that needs excess water diverted. I haven’t done a full test but the space I have is 1x1x1m and well away from any buildings. 

    I would rather use rubble, grit and stones over the crates unless the crates provide a much better benefit?

    Its only rain water that needs taken away, plus the border will have imported drainage with the stone, top soil etc 

    The water drain away fairy quick form the area I have dug
  • wild edgeswild edges Posts: 10,497
    Crates are used to capture large volumes of water when the ground doesn't soak away very quickly. A 1mx1mx1m crate will hold about 950 litres of water whereas a 1mx1mx1m hole filled with rubble hardly holds any water at all and will silt up over time. It sounds like you need more of a French drain or fin drain type of setup which takes water from the surface of one area to below ground in another. A long trench always soaks away quicker and better than a cube because it has a better surface area and doesn't saturate the soil around it as much. The best way to do it is lay a perforated pipe (minimum 100mm diameter) wrapped in geotextile in a trench that's deep enough to hit the layer of soil that soaks the water away (IE below any clay). You backfill the trench with gravel and you can always finish it off at a sump which can be your rubble filled hole.
    If you can keep your head, while those around you are losing theirs, you may not have grasped the seriousness of the situation.
  • g333g333 Posts: 125
    Sorry I should have explained more. So I have dug a trench 0.5m deep 0.5 wide and 10m long ( the length of the border)

    The plan for that area is fine gravel, perforated pipe, wrapped, back filled with gravel manure, top soil and bark.

    All the clay taken out will be dumped.

    The soak away is at the end of the garden and the pipe will lead into this. This is 1x1x1m.

    That’s the full set up so from what you said crates will do a better overall job?



  • g333g333 Posts: 125
    I was looking at the below crates, these dont seem to have an inlet hold for the pipe like some others do.  I presume you leave the pipe sitting on top of these crates once wrapped in fabric?
  • g333g333 Posts: 125
    I’m still in 2 minds with what option to go with for the soakaway

    Anyone able to share their experience or knowledge?

    option 1
    10-20mm gravel at the bottom
    4 x190l (1000x50x40mm each) crates wrapped in geo fabric (french drain pipe into here)
    back filled around and on top with 10-20mm gravel
    then soil
    bark as final layer

    option 2 
    line the hole with geo fabric
    fill with 5-10mm gravel 
    fill with 10-20mm gravel 
    french drain pipe in
    Close the geo fabic
    cover with 10-20 mm gravel
    soil
    bark as final layer

    The crates seem expensive at £40 a crate each
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