On 10/11/2011 23:52, Timothy Murphy wrote:
Nightjar wrote:

I live in a small part of a very large building (an old orphanage).
Strangely, there are no downpipes from the gutters
in the front of the 4-storey building.
All the water is transferred to downpipes at the back of the building.
Unfortunately the water goes over a valley in our part of the building.
The quantity of water after a heavy rainfall is immense;
it sounds as though a large river is running over one's head.
There is occasionally a slight leak through the ceiling at one point.

Would it be possible to extend the downpipe(s) that empty into your
valley, so that the water bypasses it?

Possibly.
The problem is that a 1-storey extension was added about 30 years ago
at the back, with the result that the water goes down onto a flat roof,
and the owner of this is concerned at this,
particularly after the exceptional downpour last month.

If you are extending the downpipe, it could also bypass the flat roof.

Colin Bignell