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Posted: Thu Jul 07, 2016 9:11 pm
by Jimmy Conway
This should possibly of been an earlier question I asked but,
Are there regulations specifying the drain capabilities of a pipe in relation to the area it hopes to drain.
I plan to drain an area that could catch approx 180m2 of rainfall into a 110mm pipe.
Calculation is belt and braces and a!lows for next doors rainfall into shared roof downpipe and probably some/most of there rainwater at ground level. Ideally neighbour would divert their own rain but sadly a fair bit of there's will run into my garden and I would rather it went down a pipe than have standing water.
Hopefully I have worded this soyou guys can understand.
Thanks
Posted: Thu Jul 07, 2016 9:24 pm
by seanandruby
Is it going into a manhole, attenuation cell or soakaway. Your neighbour should deal with there own run off. An area that large would need a couple or three gullies/drainage points. you could use ac150 dia' pipe. I have two spare cells goong cheap :;): 
Posted: Thu Jul 07, 2016 10:24 pm
by Jimmy Conway
Thanks for taking the time help sean and ruby.
Will connect to same outlet as guttering downpipes (storm)
Ideally neighbours would deal with they're rainwater but I can't see them lifting they're slabs to stop they're water running under fence and into our slabs. So rather than encouraging standing watervi think it best to deal with it head on. Both houses have a very small strip of garden chips beside house (garden slopes towards house) to give drainage but from what I've reads strip of chips isn't the greatest drainage system. Think its possible for me to lift and relay some slabs to make a "bowl" with a gully pot at centre to take away water.
Just hoping a 110mm has a high enough capacity for my needs.
My 180m2 calculation is based on two back garden and two roofs on the same side all draining to same outlet.
Thanks
Posted: Fri Jul 08, 2016 10:19 am
by seanandruby
Can't you install a linear channel?
Posted: Sun Jul 10, 2016 12:59 pm
by Tony McC
In theory, you should be able to effectively 'drain' 300m² vis a 100/110mm dia pipe, but that's it ruynning at ful bore and assumes there are no obstructions to the flow. This values is based on the 1-in-25 year storm rate.
However, if this 100/110mm pipe connects into, say, an IC with two other lines coming in, and each of them is 100/110mm, with an 100/110mm outlet, then there is a big problem. There is real potential for water to come into the IC faster than it can escape, and so the chamber will surcharge (overflow).
In such a situation, we'd look to use an outlet of 150mm or larger so that, during this hypothetical once-in-25 year event, there's no risk of surcharging.
Coming back to your situation, I'd be happier relying on 150mm dia pipework for an area of 180m², but just where is all that water going to go?
Posted: Sun Jul 10, 2016 6:08 pm
by Jimmy Conway
OK,
Two 68mm pipes connecting into approx 4 inch pipe as outlet.
Draining approx 180m2 from roofs and ground level?
I've done some exploratory digging and have made necessary connections, just need to install and connect gully pot. I'm confident that will have sufficient fall on it.
Just hope someone in the know can confirm its up to standard???
Posted: Sun Jul 10, 2016 6:16 pm
by Dave_L
110mm will be fine
Posted: Sun Jul 10, 2016 6:27 pm
by Jimmy Conway
Thanks. That puts my mind at rest.
Thanks to everyone who's replied (too what's probably a very boring topic)!!!!