Plastic downpipe union with cast iron downpipe

[Harry_W]

The area near my back door regularly flood with rain water from a plastic downpipe. How can I divert the water into the original cast iron downpipe? Do I need to totally remove the original downpipe first? Is there a way of joining them up?

Here's a photo:

 

[Ian H]

You could fit a gully at ground level and junction that into the drain, it would also take any surface water that lands there.

Or you could join the pipes high up somewhere.

 

[Harry_W]

If I removed all the old downpipe, could I use something like this to connect the plastic to the drain?

 

[Ian H]

No, you would want an internal drain connector for the bottom connection, a DC115 bandseal for the top connection and a couple of 45degrees bends between them.

What do they look like at the top?

 

[bobasd]

if its flooding somethin is blocked.
good idea to run to a new gulley but if it was my job heres how i would do it.

i'd remove both the plastic and CI pipes. and then open up the concrete for a new gulley away from the alcove. i'd clear the drainage set and connect the gulley and swing over a new plastic down pipe from the gutter outlet to drop into the gulley.

look at the bubbling on the brickwork.waters getting into the bricks and blowing the paint.
its possible that there is a concreted over old gulley hidden below the surface. if there is it has to be dug out and the new gulley set level with the surface.

worst case is no below ground drainage pipe.if thats the case then come back here

 

[Harry_W]

I haven't got any photos of above but the CI pipe is broken above anyway so needs to be removed. The flooding is due to a flat roof adjacent not having proper guttering and a broken downpipe from the house next door leaking onto the flat roof! I like the idea of just taking out the CI pipe and putting a bend in the plastic downpipe and connecting it with the drain.

I'll take the slabs up to have a look for a gulley anyway so thanks for the heads up.