I make no apologies for the quality - this is the first time I've tried this.
This is a cheap waterproof USB camera tied to a wire-coil type drain clearing wire and poked down a rainwater drain:
The camera was this:
There's a yellow hose down there too - party to keep washing the camera lens and partly to measure flow.
Long and short of it:
The drain pipe seems to be a bit of 68mm black plastic running about 7m until it arrives under the front lawn. That's as far as the hose would go.
The camera went in 4.75m (lead length minus a bit to reach the laptop).
The pipe was clear for those 4.75m but not running free.
The camera is at a slight tilt due to the way I tie wrapped it to the drain clearing wire.
Later on in the vid you can see wash-back from whatever the hose hit (probably a silted up soakaway).
Better than the other 3 downpipes. One was blocked and the other two terminated in a hole 6" under the concrete right by the hose wall. Might have been like that forever - did not look like the pipe had rusted away.
Won't be using those.
Might use the one in the vid - if necessary only. Rought idea where the pipe is under the lawn - owuld need to dig a new soakway.
However, I found an option to connect to the main sewer that looks quite easy. Will see if that is sufficient first.
Cheers
Tim