What ho one and all,

The land for my house has a fall of around3-4 meters, front to back over about 50 m. Rainwater from the roundabout in front tends to drain onto my land a prior to building, sort of 'flooded' the front garden.

During the build, I installed a sump on the verge and took a underground drainage to the woodland at the rear of the garden. Unfortunately, I did not take photographs. Although buried on my land, the actual outlet was on the surface in the woods so that water could drain out. But 1,2, 3, or 4 meters from my boundary? Beats me?

Nowadays, the water does drain away, and then the flooding starts again. I think the outlet in the woodland has become blocked with leaves, twigs and perhaps 'someone' has made a home there. I would like to find the outlet but uncertain where it is, and it is certainly now covered with brambles, fallen branches, etc.

My question is, what would be the best way to find the outlet without actually clearing everything and digging where I 'think' it may be?

Thanks and toodle pip

I'd be tempted to put some brightly coloured liquid in at the top and see whether you can see it at the bottom. I suspect blockages are not likely to be total. PiH's idea is also a good one.

Dye will only work if the water can be seen on the ground - in which case I would expect to see surface water or at least a very damp patch which of course would indicate the drain outlet anyway.

It might be a bit late in the year but I would expect to see a difference in the vegetation where there is additional water to that of the surrounding area.

Thanks for the suggestions. If memory serves me correctly, it is the 4" Wavin coil pipe. Unlikely to be blocked somewhere in it's length for two reasons. In the sump, I have a plastic vegetable strainer around the pipe entrance to prevent any large debris getting into the pipe and blocking it. Additionally, when installed, the exit from the sump is a smaller diameter pipe than the overall length, which is probably 4".

Not really possible to see any dampness around the exit as after 13 years, there is so much growth! Additionally, the exit area was always damp / wet. But I do like that idea of a coloured liquid or dye. Will investigate that.

Tonight, I wondered about smoke. Put one of those smoke bombs into my wet/dry vac, use the blow side of the vac and 'blast' the smoke into the pipe. Don't know if it would go 50m +.

If it is the flexi land drain pipe then as GreenPaddy says silting up is likely. They can be difficult to clean and any rods used will need to have a rounded end otherwise they will get stuck on the corrugations.

I have a land drain pipe which I clean with a length of 25mm PE water pipe with the end rounded with the help of a heat gun and I connect a hose pipe to the outboard end so that the land drain pipe was flushed out. (Best done from the down hill side). I've not had much success with traditional rodding as the corrugations and structure of the pipe made this v. difficult.

The bad news is that the pipe I am citing worked fine for 10 years or so but once it silted up flushing through appears to be a 2 -3 year job. I guess flushing only removes some of the silt and it never gets back to new state.

Over here there are drainage contractors who come along with their van which has a hose with various ends connected to a high pressure pump which they use to blast blockages out but the expectation is that once 'liquefied' the blockage runs down the drain, this might work, you would have to talk to the contractors. The same people have cameras that can inspect the pipe internally and thus locate blockages or other failures.

In your place I would start with the 25mm PE water pipe option and go from there. (garden hose is not rigid enough)