On Aug 22, 8:36 am, The Natural Philosopher wrote:
croxley wrote:
I am replacing the guttering on a flat roof in London using deep fill
gutters . It is about 80sq mtr. It is going to be diffucult to give it more
than one 75mm downpipe.

Is that likely to be adequate?

I cant remember but the Osma site - google it - has specs.

http://content.wavin.com/WAXGB.NSF/pages/RWRoofAreaCalculationsEN/$FILE/RainwaterGuide5.pdf

In that case it says that Roundline should do the job for a 79 sq
metre roof. I assume that Roundline is 75mm, I can't seem to find that
easily.

I am puzzled why the site says "Multiply the roof plan area by the
roof pitch factor" in order to get the actual roof area. Why do you
need to know the actual roof area for rainfall calculations? Surely
the plan area should be used.