Drainage when there are no drains to drain into

[d000hg]

Putting a log cabin in the middle of our garden, there are no drains into which we can connect so I'm wondering the typical/best option(s) here. We'd want to put guttering on, and a large water-butt which would act as a reservoir/buffer but in heavy rain will of course fill and overflow unless it's ridiculously large. We're talking about ~70m^2 footprint, situated in the middle of a big lawned paddock area.

Is this where a soakaway is typically used and if so, can anyone advise on how to design and construct it? We do have a digger coming on site so any groundworks are probably quite easy to get done.

Thanks.

 

[d000hg]

On a completely separate thread I saw this quote:

The regulations require rainwater to be discharged in a specific order

• into the ground (including RW harvesting)
  
• into a watercourse
• into existing RW drains

You can't use the next on the list unless the preceding one is not possible.

So I guess there are specific regs on this as well, you can't just figure out something you think is good enough?

 

[JP_]

Yeah, just dig a soakaway hole.

 

[d000hg]

Yeah, just dig a soakaway hole.

Is this literally just a big hole that you set a drain into, then back-fill with rock, then connect your drainpipe? Or do you not even have to bury a pipe but can drain straight onto the top? My only experience looking into soakaways is in relation to septic tanks, but I gather that's quite different.

Any rules of thumb on size/construction?

 

[d000hg]

Googling found this which is geared to selling their product: https://www.drainagepipe.co.uk/soak...ow-do-i-know-what-size-my-soakaway-should-be/

I hadn't considered the need for caging the soakaway, but their calculation is basically soakaway_volume = roof_area/50 (using m^2 and m^3) units. If anyone has any thoughts on that do share.

EDIT: oh, am I right that this product uses un-filled cages, to create a 'cave' underground? I had initially assumed they'd be filled with rocks like those river-bank protection systems.

 

[JP_]

Yeah, you put in some big plastic crates, cover with membrane to stop silt. drain pipe/s go into the side. Then cover with whatever you want - I have a patio on top of mine. Best not to plant anything that will grow big on top, you don't want roots breaking the silt membrane. You can always feed it from a water butt too, so it's just overflow.

 

[Notch7]

Googling found this which is geared to selling their product: https://www.drainagepipe.co.uk/soak...ow-do-i-know-what-size-my-soakaway-should-be/

I hadn't considered the need for caging the soakaway, but their calculation is basically soakaway_volume = roof_area/50 (using m^2 and m^3) units. If anyone has any thoughts on that do share.

EDIT: oh, am I right that this product uses un-filled cages, to create a 'cave' underground? I had initially assumed they'd be filled with rocks like those river-bank protection systems.

Crates have something like 95% capacity, far higher than rubble filled soakwways.
They are basically like milk crates -plastic boxes that can support the ground above.

I think they are usually cable tied together then wrapped in geotextile material like terram.

There are numerous layout options.

 

[d000hg]

Cheers. I've not seen these before. Is this now the normal way of doing it, or is filling a big hole with old bricks still viable/common?

 

[Nige F]

, or is filling a big hole with old bricks still viable/common?

Only if you've got a load of rubble to get rid of and can dig a big enough hole to allow for the rubble being non absorbent.

 

[StephenOak]

By no means an expert but I thought that crates were the normal way nowadays as the soakaway is a lot smaller. As Notch says with crates the water can fill 95% of the volume, with a rubble fill it is a lot less, maybe 50%, maybe less than that. So the hole that you have to dig is twice (or more) the size.

 

[d000hg]

Yeah the concept totally makes sense, these things must be STRONG. I guess since they are hollow you can view them as a tank and even maintain access to them... say you did start to get silt building up you could hoover it out?

 

[d000hg]

Only if you've got a load of rubble to get rid of and can dig a big enough hole to allow for the rubble being non absorbent.

I mean I do have the space... hundreds of square metres. But you'd presumably have to dig it out and re-lay every N years as all the gaps get filled up with soil?

 

[StephenOak]

Again, not an expert, but I think that maintenance on a soakaway is a bit of a contradiction in terms. The pipes leading to it and the soakaway itself are not inches but feet underground. So to gain any sort of access you need to dig quite a big hole.

Hence they are wrapped (double wrapped?) in protective material to stop silt getting in for the life of the soakaway.

If you did dig a hole to gain access, unless you completely uncovered the soakaway you would need to cut through that material. Even if you apply an overlapping patch afterwards that will surely make that protection less effective in future.

A set of crates is sort of like a tank but has a couple of advantages. The individual crates are easier to move and can be arranged in the appropriate shape to suit the situation. Also a tank has to be strong enough to take all of the weight of the overlying soil, most especially in the middle of the top, whereas each crate only has to take the weight of the soil on top of it.

Edit: You have the space for a larger one but not only do many people not have the space, a larger one means more soil (sub-soil, etc) to dispose of and that is expensive nowadays.

 

[d000hg]

Yeah good point, the individual crates are not huge so there's a lot more strength there than I maybe thought.

Thanks for the comprehensive reply