Flat roof drainage

Hi all,
A question on flat roofs and how rainwater is drain from them.
What is the standard way to drain water off a flat roof?
I have a single-storey extension on my property which has a flat roof. There is gutter running along one end of the roof and a downpipe at one corner. It appears that there are a couple of pipes running through the 'lip' at the edge of the roof and into the gutter. Rainwater run through the pipes (from roof-outlets?), into the gutter and down to the drain. Does this sounds like a standard construction?
The reason for the question is that I've just had the guttering replaced by a large windows/fascias/gutters company in the South-East (not naming names yet!) The two pipes now no longer run into the (new) gutter since this is above the level of the pipes, nstead rainwater now pours through the pipes and down the side of the house! Really just wondering if the construction of the extension is so wacky that the fitters didn't realise what the pipes were?
Thanks in advance!
Colin
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Get them back to reposition the gutter.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.