Hi, gutter and downpipe efficiency question.

[Mattba]

On bigger shed roof areas would putting 2 spitters close together into a 90 deg bend and T Junction and then downpipe significantly increase the capacity of that length of gutter and downpipe?
On open sheds we run the downpipe down the shed column, and there can be very large sq/m of roof to cater for in one downpipe.
TIA.
Matt.

 

[Chuck]

Drains aren't really my thing, but as no-one else has answered I'll try to get the ball rolling.

Using Floplast systems as an example,

https://www.floplast.co.uk/uploads/related-documents/TISrrAkBGW14aNNTDq0lvzHhdJmD1xziuzMTQoJY.pdf

the flow capacity with a running outlet at the centre of a gutter is typically within 10% that of two half-length gutters with stop end outlets. Usually higher but one example in their tables is actually lower. The 90° bend and T-junction you're going to need for your scheme might reduce the capacity depending on how close they are to the outlets.

TBH, if your scheme worked effectively I think you'd see it used fairly often and/or you'd be able to buy a 'dual outlet' to implement it.

 

[Ric2013]

TBH, if your scheme worked effectively I think you'd see it used fairly often and/or you'd be able to buy a 'dual outlet' to implement it.

Unlikely IMO as it would be unusual and then people would delight in saying it was 'wrong' even if it worked.

That aside, I agree with you in that the downpipe almost never runs full-bore and the capacity is usually limited by the ability of the gutter to discharge into the pipe without overflowing. A running outlet can receive water from both sides, but between the two running outlets, there is nil flow, so there would be hardly any advantage in having two running outlets instead of one (as you say, it'd be much like having two stopend outlets).

Realistically, if the gutter is laid to the correct fall, we have over 100 sq m for a 68mm downpipe: enough for 3 houses the size of my own, so I wonder what the OP meant by 'sheds'.