We’ve successfully negotiated putting our rainwater, via attenuation storage, into the sewer (long story but no room for soakaway). I now need to figure out options for how we get it from each downpipe into the attenuation crates.

Initial plan was a slot/channel drain with localised ‘shoes’ connecting into it at each downpipe. Visually though, the preference would be a simple French drain, geotextile lining with a perforated pipe coil below gravel. The weakness I see with the latter approach is ‘reverse drainage’ whereby we end up with the rainwater off our roof saturating our foundations before it percolates down into the pipe...

What I’m wondering now is if there’s anything out there that could do both. Some form of channel with grating that’s then buried under gravel, so water can either trickle down off the facade or be directed down off the roof.

Anyone got any ideas/product links or am I over thinking this?

How about an hybrid system: surface drain with slotted cover (vehicular type as necessary); knock out the bottom of the resin channel, so that the water escapes into the gravel course, then down into the French drain which discharges to manhole.

The fall connects directly into the surface drain (vertically, no shoe) - for this, a cut-out is required in the cover...


P.S. Watch out for slotted covers in front of building entrances etc. as they can catch out stick- or crutch-users...

gg

Posted By: djhWhy not just connect each downpipe to a drain pipe that goes to the attenuation crates? Multiple downpipes can share a single drain if convenient and sized properly. Then have a separate French drain if desired.

It just seems like doubling up - the attenuation is a block of crates adjacent to the house (imagine an exclamation mark on its side, our house is the dash and the crates are the dot). In other words the direction and location the roof draining pipes would run around the house is the same as the French drain so they’d naturally sit above each other anyway.

I think Peter’s solution is probably the most workable but I don’t know if the flow rates along a perforated pipe would be dramatically different to the channel drain that our drainage design was based on.

Perhaps check out Fin drains using non-permeable geotextiles...

http://www.pavingexpert.com/drain07.htm

Not used them myself. We went for regular linear drains for the patio. Where I built a French drain around a shed I have problems with leaves rotting on top of the gravel causing weeds and grass to grow. Looks untidy and hard to mow over due to the stones.

110mm half perforated pipe..

https://www.draindepot.co.uk/110mm-x-3m-single-socket-half-perforated-soakaway-pipe.html

I plan to have my downpipes finish above ground level with a shoe and discharge into a gravel strip/French drain that surrounds the house. The French drain will have a perforated pipe at the bottom which may or may not end up carrying the water but guarantees a flow rate similar to a standard pipe.

The French drain can be connected to the storage crate via the perforated pipe(s) and the granular fill of the French drain which should be contiguous with the granular fill surrounding the crate (which will be covered by geo-membrane to prevent the fill getting into the crate). In this way water in the granular fill and water in the perforated pipe go into the store.

A little easier for me as I have piles so there is little need to move the water away from the foundations.

I am struggling to hold back the quip!!

<blockquote>Thanks CWatters, I think that's what I envisaged our contractor will put in anyway but their recent description of it as a 'coil' suggests it might be something more loose laid and flexible than that. Will check with them.</blockquote>

Think I'd want the twin wall stuff as a minimum.