Drainage...

[Jim2]

Sorry to cross post but do any of you paving chaps have any ideas on the soakaway type selection I should go for that I asked about here:

http://ext.pavingexpert.com/cgi-bin....t=10009

Building control are good with either type but I would like to calculate how big the infiltration drain needs to be to work out which will be the best way to go.

[local patios and driveway]

Hi jim sorry your last thread was ignored, thats annoying when you are looking for solid advice, got to say for me i would be using storm crates for a soakaway, its hassle free, solid and simple in construction. I think four of them is a 1m sq probably going to cost you maybe 140 sovs delivered but its a good system

[Jim2]

Thanks are the storm crates suitable to be fitted under the drive? The drive slope is around 12% across site and 2% towards the road if that makes a difference.

My concern with the storm crate is the excavation depth as I think just about the only place it can realistically go is directly above the main sewer and vaguely in line with the incoming water supply.

Just as a point of interest how do you size an infiltration drain?

[Pablo]

another option would be to pipe the water to a small chamber that's out of the way of all the services etc then pump the water into the stormwater system. It should cost about the same but the chances of sinkage are much less. Between you and me I'd also not involve building control any further.

[Bob_A]

Hello Jim
I'm just a diyer so I can't give expert advise but I can tell you what I have and my experience.
I have a 58sq metre patio that drains into one of those ditches.
The ditch runs along the longest edge of the patio that is 8m long.
I can't remember exactly but I think I made the ditch 750mm deep and 250mm wide.
At the bottom I laid two 9" perforated pipes one on top of the other.
9" pipes are quite big, I don't think I needed two or them to be 9" only reason I used them is that they were free.

I live in London where the first foot of soil is really good quality but then it starts to turn to clay.
It's been there for around two years and so far no problems.

My patio is Indian Sandstone which is riven, your drive will be blocks that are smooth, not sure if that'll make a difference?

[Jim2]

Well I spoke to the BCO chaps again and they are happy with 400mm deep x 200mm wide infiltration drain with a 100mm perforated pipe in the bottom. I really don't understand why I can have a 0.4m3 infiltration drain which is filled with gravel when if I use storm crates I need 0.8m3 of clear volume. Can anyone shed any light on this?

[DNgroundworks]

yea i can - building control are hopeless

[DNgroundworks]

And clueless, regarding the subject in question :p

[lutonlagerlout]

^^ what dan said
LLL

[Jim2]

In that case will there be any probs using the 400x 200 solution?:-)

[Bob_A]

I'm not an expert but why not use two pipes.
Also dig deeper as I believe reading somewhere depth is more important than width
Can't do any harm can it?