Surface water drainage

[soggy]

I'm trying to decide what to do with the rain water from my new conservatory roof. Its gutters are below the house gutters, which run to a downpipe at the far side of the bungalow. Pipes from the conservatory gutters to the side downpipe would have to run across windows and a patio door. There are no drains at the rear of the property because it's built up above the garden and all the drains run to the front.
I dug a pit in the garden for a soakaway and ended up with a sump. The water level is never more than a foot from the surface, and when it rains hard it comes to the surface and parts of the garden run with water, though it does drain away reasonably quickly.
Three options occur to me: I can take the conservatory down pipe into a small hopper piped to the sump. The end of the underground pipe will be under water most of the time, but the ground slopes away so that the sump will overflow before the hopper can, so at least the water is taken away from the house.
Alternatively, I could with considerable effort excavate a 30 yard trench in sticky clay full of rocks, through dense shrubbery and down to the bottom of the garden. What to do here is a puzzle though, because although there is a stream it's a couple of feet inside my neighbour's garden, and the bottom of my garden slopes up slightly before dropping down to the stream (and is full of tree roots). It seems an enormous effort for a drop of rainwater.
Or I can let the downpipe discharge onto the ground and lay paving around the conservatory with a fall towards the garden. At present the conservatory is surrounded by soil, so I want some kind of paving, which no doubt will add to the runoff problems.
None of these options seems ideal. Any suggestions?

[84-1094545549]

The 30 yard trench is favourite, in my book.

You don't need to go terribly deep, just 300-450mm or so, and then install a simple land drain that will deliver the water from conservatory roof down to somewhere near that stream. Although you can't dig all the way and outfall directly into the stream, as it's on the neighbour's property, if you terminate the land drain as close to the stream as poss, and run a length parallel to the stream for a few metres, gravity and natural seepage will do the rest.

The ideal scenario would be solid pipe collecting the roof water via a hopper and carrying it beneath the patio to a point in the garden/lawn where some sort of soakaway can be constructed, even though it's about as much use as a chocolate fireguard. The outlet from the comedy soakaway is the land drain that leads down towards the stream, terminating in the parallel run that is intended to help disperse any surplus water as effectively as possible.

[soggy]

Thanks Tony, I was afraid you'd say that! Actually, there's already a land drain going across the bottom of the garden, so the perforated pipe from the comedy soakaway can lead to that.

Rob

[soggy]

I've been thinking... (things happen slowly around here, especially the thinking).
I can't see the point in keeping the comedy soakaway, especially as it would need lining with concrete rings or whatever, and a strong cover. It seems like more expense and effort to no purpose.
Were you thinking of it as a small attenuation tank? As it's usually full to within six inches of the surface I think it would have to be a lot bigger to achieve this.
What I'm thinking now is: fill in the useless sump.
Install bottle gully with silt trap in the paving under the downpipe, a couple of 45º bends to get down to 300mm or so, then flexible perforated plastic land drain all the way down to the end of the garden.
The side garden path is 6' x 18" concrete slabs which I've lifted to dig the trench more easily instead of hacking through the shrubbery. Will flexible pipe be OK under the path when I put it back?

[Tony McC]

Yes, but make sure it's well surrounded with pea gravel, or similar, and I prefer to envelop both collector and dispersal drains with a geo-membrane to keep the silt out.