Fixing my run-off drainage

adocholiday

Hi all,

I have a significant issue with drainage at one side of my house, which is mainly caused by the run off from a single downpipe. I've known about this issue for a while, but the rain over the past few days has given me the kick up the backside to sort it out.

The first image shows the layout. We basically have 3 structures each with their own roof (grey areas), and there's a fiberglass valley between them (purple area). The valleys run off into gutters either side, each with their own 3 inch downpipe (red areas) into standard 4-inch PVC pipes (orange arrows) which all connect to a single 4-inch pipe that runs to a soakaway down the garden. For illustration, the green is lawn and the yellow area is a mix of paving, concrete etc., hard surfaces basically.

The area I'm having significant drainage issues with is the dashed box, in particular the drain closest to the roof valley. This drain overflows in even moderate rain, and the water pools in the area significantly. When that drain backs up then the one up-flow from it does too, and then that water also runs off into the lawn making everything worse. During the recent rainfall I had a 2-inch deep pool of water sitting against that entire wall of the house which has since drained away. There is a thin section of gravel between the lawn and the house, the lawn doesn't sit directly against the foundation, but it still can't be good but I'm also considering improving that as part of this overhaul. None of the other drains have issues they can handle any rain that's been thrown at them so far. I checked the problematic one for blockages but there doesn't appear to be any. I ran the hose into the drain, lifted the drain cover further down and saw the water flow through with no issue. I've included some pictures which hopefully adequately show the setup. The only thing jumping out at me is it looks like there's a P-trap on that particular hopper, visible in the first picture, and I wonder if that's having something to do with it.

All images are here: https://imgur.com/a/FYjuiiw

I'd be interested to hear any advice or suggestions for DIY'ing this, because I'm sure there's a simple fix. Cheers.

10-10-20

Hi, I think from looking at the images that it's related to fall on the pipes, they appear to be installed very high in the soil and this makes me think that they are laid on the foundations or over another obstruction between the rear and the run-off to the soakaway. If you probe with a metal rod, can you identify that obstruction or gauge the depth and or fall?

standardg60

You really need to see what's happening all along the pipework during the overflow. Next time it happens, lift every drain cover along the line. I would wonder if it's the actual soakaway that's backing up everything. Soakaways are just that, they're designed to slowly drain water, fill them quickly and they're useless. In your pic the water level in the 4 inch pipe is lower than the lip so it's not a trap issue.

adocholiday

https://www.boards.ie/discussion/comment/121279185#Comment_121279185

Thanks for the input. I haven't probed the area around the pipe but will do that tomorrow. The pipe itself is fairly deep, measuring tape says 12 inches or so.

https://www.boards.ie/discussion/comment/121279514#Comment_121279514

Not sure that it's an issue with the soakaway because none of the other drains back up like that, it's just that one. Some are even more shallow than that one and downslope of it. The soakaway is 40m from that pipe and about 2m below (long steep driveway). The water level does drop when the rain stops, but slowly.