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UK diy (uk.d-i-y) For the discussion of all topics related to diy (do-it-yourself) in the UK. All levels of experience and proficency are welcome to join in to ask questions or offer solutions. |
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#1
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Size of a soakaway
Anyone have any idea of a formula to use constructing a soakaway?
Googling around gave: Vol(m3) = Area to drain(m2) × (rainfall rate(assumed 50mm/hr)/3000) Which in the example gave 60m2 needing 1m3 size, but I only need about 4m2 which gives 7cm3, which sounds too small. any ideas? Steve |
#2
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Size of a soakaway
"Steve" wrote in message ... Anyone have any idea of a formula to use constructing a soakaway? Googling around gave: Vol(m3) = Area to drain(m2) × (rainfall rate(assumed 50mm/hr)/3000) Which in the example gave 60m2 needing 1m3 size, but I only need about 4m2 which gives 7cm3, which sounds too small. any ideas? 7cm is about a spoonful so maybe a bit on the small side. The 50mm times the roof area is correct. 4m² *50mm = 0.2m³ This is for the volume of the void, so it depends on what you are back filling the soakaway with, how big the hole should be. mark |
#3
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Size of a soakaway
"Steve" wrote in message
... Anyone have any idea of a formula to use constructing a soakaway? Googling around gave: Vol(m3) = Area to drain(m2) × (rainfall rate(assumed 50mm/hr)/3000) Which in the example gave 60m2 needing 1m3 size, but I only need about 4m2 which gives 7cm3, which sounds too small. any ideas? Steve Tell me you're joking, right? A soakaway for 4m2? It's not going to produce enough water to worry about. Anyway if you really want to dig a hole try an upturned (clay) flowerpot. Remember a soakaway is only a buffer to hold the water until it can, guess what... soak away so you're not going to need to hold very much. |
#4
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Size of a soakaway
On Apr 14, 5:10*pm, Steve wrote:
Anyone have any idea of a formula to use constructing a soakaway? Googling around gave: Vol(m3) = Area to drain(m2) × (rainfall rate(assumed 50mm/hr)/3000) Which in the example gave 60m2 needing 1m3 size, but I only need about 4m2 which gives 7cm3, which sounds too small. any ideas? www.pavingexpert.com, specifically http://www.pavingexpert.com/drain08.html Note that to size a soakaway properly, you need to know how porous your soil is. Someone living on sand/gravel can just connect a downpipe into the ground, someone living on heavy clay is going to need a major piece of engineering to support the required hole. |
#5
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Size of a soakaway
Steve wrote:
Anyone have any idea of a formula to use constructing a soakaway? Googling around gave: Vol(m3) = Area to drain(m2) × (rainfall rate(assumed 50mm/hr)/3000) Which in the example gave 60m2 needing 1m3 size, but I only need about 4m2 which gives 7cm3, which sounds too small. any ideas? Steve Anything less than 10m2 doesn't need a soakaway, just dig a small hole, stack bricks in pairs (with holes in) about 5 high, so ten bricks will do it. Cover with a few shovelfuls of gravel and forget about it. -- Phil L RSRL Tipster Of The Year 2008 |
#6
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Size of a soakaway
On Tue, 14 Apr 2009 21:55:53 GMT, Phil L wrote:
Steve wrote: [12 quoted lines suppressed] Anything less than 10m2 doesn't need a soakaway, just dig a small hole, stack bricks in pairs (with holes in) about 5 high, so ten bricks will do it. Cover with a few shovelfuls of gravel and forget about it. Thanks all, I'll throw something simple together. Its actually more of a precaution, I'm seeing some damp on a party wall (below dpc below floor level for next doors garage), the downpipe from the conservatory is right next to the point where it seems to come from, and I cannot see the bottom of the downpipe so I'm improving dranage just in case. Presently it flows about 5M away from the downpipe but just terminates into soil. Steve |
#7
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Size of a soakaway
"Steve" wrote in message ... Anyone have any idea of a formula to use constructing a soakaway? Googling around gave: Vol(m3) = Area to drain(m2) × (rainfall rate(assumed 50mm/hr)/3000) Which in the example gave 60m2 needing 1m3 size, but I only need about 4m2 which gives 7cm3, which sounds too small. any ideas? Steve Years ago I remember checking the ground for a soakaway for a septic tank, it was a bit clayee so the procedure was to dig a 1 metre cube hole in the ground, fill it with water and check how long it took to drain away, on that basis it was decided how large the soakaway had to be, it was a very long time ago and I cannot remember any more detail or where the procedure information came from but I would imagine that there may be a similar procedure for surface water soakaways, albeit a larger volume of water to get rid of. Cheers Don |
#8
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Size of a soakaway
On Apr 14, 5:42*pm, "mark" wrote:
"Steve" wrote in message ... Anyone have any idea of a formula to use constructing a soakaway? Googling around gave: Vol(m3) = Area to drain(m2) × (rainfall rate(assumed 50mm/hr)/3000) Which in the example gave 60m2 needing 1m3 size, but I only need about 4m2 which gives 7cm3, which sounds too small. any ideas? 7cm *is about a spoonful so maybe a bit on the small side. The 50mm times the roof area is correct. 4m² *50mm = 0.2m³ So the soakaway needs to hold the water from the roof when 50mm of rain falls in one downpour. Robert |
#9
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Size of a soakaway
Steve wrote:
Anyone have any idea of a formula to use constructing a soakaway? Googling around gave: Vol(m3) = Area to drain(m2) × (rainfall rate(assumed 50mm/hr)/3000) Which in the example gave 60m2 needing 1m3 size, but I only need about 4m2 Do you really mean 4m^2, as in 2m x 2m? |
#10
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Size of a soakaway
"RobertL" wrote in message ... On Apr 14, 5:42 pm, "mark" wrote: "Steve" wrote in message ... Anyone have any idea of a formula to use constructing a soakaway? Googling around gave: Vol(m3) = Area to drain(m2) × (rainfall rate(assumed 50mm/hr)/3000) Which in the example gave 60m2 needing 1m3 size, but I only need about 4m2 which gives 7cm3, which sounds too small. any ideas? 7cm is about a spoonful so maybe a bit on the small side. The 50mm times the roof area is correct. 4m² *50mm = 0.2m³ So the soakaway needs to hold the water from the roof when 50mm of rain falls in one downpour. Yes, but 50mm is quite extreme. mark |
#11
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Size of a soakaway
On Wed, 15 Apr 2009 07:47:10 +0100, Steve wrote:
Its actually more of a precaution, I'm seeing some damp on a party wall (below dpc below floor level for next doors garage), the downpipe from the conservatory is right next to the point where it seems to come from, and I cannot see the bottom of the downpipe so I'm improving dranage just in case. Presently it flows about 5M away from the downpipe but just terminates into soil. When I built our conservatory I needed a soakaway for the 5mx3m roof. Without knowing the calculations, and knowing that we wanted a 12" gravel border all round it, I improvised. The 5m border of the conservatory furthest from the house was dug out to about 24" deep, 12" wide all the way along (done while we had a local by- the-hour mini digger in to do the foundation pads for the steel suspended floor). Then I lined it with landscaping fabric, 20" of cheap coarse gravel/small stones, another layer of landscaping fabric then 4" of decorative gravel. The two downspouts from the conservatory roof just go onto the top. I was worried it might silt up over time but it's been there about 10 years now with no problems at all. |
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