Drainage from a lead valley, redirection opinions

[dgardn2013]

Hi Everyone,

I own a flat conversion in an 1873 built railway house. Who ever converted it didnt have a clue as 10 years after buying the place im still finding problems with things that weren't done right. The latest is a down pipe that drains rain water from a lead valley between 2 pitched roofs, direct onto the flat roof/patio. I have been told this should never have been done the way it was due to the flat roof not being designed for so much water. It tends to puddle badly in heavy rain and takes ages to drain away.

I have added to crude pictures of how it is now, and what i propose to do. Assuming it will work, im no expert but i think it should work.

My plan is to branch out of the downpipe from the valley, and connect 2 either 32mm or 40mm pipes. Run them across the bottom of my wall and under where my door ledge overhangs. there is a small wall at the top of the stairwell, with a downpipe from the gutters straight into the drainage system. I plan to take the smaller pipes through the wall and enter the existing downpipe.

What are your thoughts please? i know the regulations etc about drainage. But since its rainwater draining into another rain water down pipe i don't believe there's a problem there.

My thinking was the primary pipe that exits the bottom of the downpipe should cope with certain downpours on its own. If its particularly heavy downpour, it will back up and start draining trough the pipe connected to the tee piece, so it acts as a safe guard. Both pipes together, are close to the 68mm pipes, and exceed the capacity if i use 40mm.

Its not possible to run a pipe the opposite direction, as that's where the gas mains come up and into the properties. So both pipes will need to run as per my diagrams. Eventually i plan to clad the a few feet up the wall to hide the pipes, and cables etc that enter there. I have no proper pics, as i rent the place out and wont be going there for a while.

Any advice would be really appreciated.

Thanks
Darren

Untitled

• dgardn2013
• 14 Sep 2013
• 1

Untitled

• dgardn2013
• 14 Sep 2013
• 1

 

[denso13]

40mm is very small for rainwater, even 2 of them. One 40mm pipe is only 1/3 the cross area of 68mm therefore even 2 pipes will carry much less water. Why not use 68mm all the way?

 

[dgardn2012]

My original plan was to use 68mm but that will stick out around 2cm under the door ledge. Which isnt so bad but when you add brackets is sticks out considerably more. If there is a way to hold the pipe tight to the wall, it may be a possibility. Any ideas?

 

[denso13]

Saddle clips are what you need //www.diynot.com/forums/roofing-guttering/uk-source-of-68mm-downpipe-clips-zero-offset.327949/

 

[dgardn2012]

Thanks, this may be the way to go after all. I can try and fasten a piece of wood or something under the ledge although i cant see 2cms poking out will make any difference. The ledge only acts as a weather strip i think and never gets stepped on. I have seen videos on you tube about bending upvc pipes, will this method work on 68mm? I have a heat gun already, and there will be some none standard angles to contend with. Or are there any fittings that you can rotate at angles? I have seen these for 32 and 40mm but not for 68mm. If i can bend the pipe i can get around the problem

 

[Hugh Jaleak]

If you reduce 68mm to 32 or even 40mm I think you'll soon find problems as the pipe will block up where it reduces in size. Secondly, there are no fittings manufactured to adapt 68mm rainwater to any size of waste pipe. (50mm miniline rainwater and 50mm waste are not compatible, there is a difference in the O.D. of the pipes.)

I would run the lot in 68mm, if angles are awkward then two bends may be needed to achieve desired turn.