Improving small soakaway - best size/shape of material to use?

[jkn]

Hi all we have a small paved area in a corner of our property which get's a lot of rainfall. There is a small 'soakaway' (not sure if that is the correct term) in a corner of this area, leading to the main drain.

By 'soakaway' ... it is an area about 10inches square, with no paving, filled with bits of stones and old concrete, and with a grille on top. The distance to the main is probably only a meter or so.

This area has been flooding in the recent torrents and I can see that water is not draining via the soakaway very quickly. Digging it out, it seems to be fairly 'silted up', which I guess accounts for this.

I'd like to improve the drainage here. I can dig out the stones, wash off the silt, and replace, but I wonder if there is more I could do. The fill material is a mixture of larger lumps of old concrete (a few inches across), and smaller round pebbles (I probably put some of this down myself, the remains of a bag of decorative gravel)

Is there a 'best size' and 'best shape' of fill material for this kind of thing?

Thanks, J^n

[Jeff Gaines]

If it goes to a surface water drain then you just need to plumb it in properly. If it's a sneaky way of putting rain down the sewer then it need something more fundamental.

[Chris Hogg]

Largish lumps of concrete occupy solid volume that would otherwise be available for water to drain through. Having just dug a small soakaway for rain running off a garden shed, I filled it with 2-3cm rounded/oval pebbles. But if your soakaway leads to the main drain, is it really a soakaway, or just a gully designed to catch silt and sand before it gets into the main drain. The Paving Expert has lots of useful information on such a topic:

[Colin Bignell]

You can buy specially designed soakaway crates:

[charles]

Important, don't put rainwater into a "main" (sewage) drain. That's what overloads the system and cause overflows of sewage.

[John J]

Save yourself a lot of angst. Install a gully and bury a bit of drainage pipe from there to the drain. If you want you can backfill the trench with gravel. 3/4" should do nicely

[John J]

I discovered that our village hall had been paying a charge for disposal of surface water to a combined sewer for years, all the while suffering backing up of water onto the car park. The old drains were excavated and found to be collapsed en route to the sewer. They have been renewed now and the car park remains clear of the traditional wading exercises

[jkn]

slight update ... I think I misspoke if I gave the impression this feeds to the sewage drain. AFAIK it goes to the surface water drain (ie. the same place as the nearby gutters).

I think my question then starts to be... how can I fit soakaway crates to such a small opening (10 inches square)? I guess I could buy a larger one and cut it down? I appreciate the need to wrap in membrane etc ... I have been reading the pavingexpert.com website as well...

Thanks, J^n

[Animal]

Firstly, 10" square is tiny, it won't achieve a lot. Milk crates, mushroom trays or other plastic hollow holey things are the best option, no point paying for anything. Cover them with scrap cloth to slow them silting up. If you can make the hole much bigger, do. Gravel or garbage is a more traditional fill, works but with less capacity.

[jkn]

Thanks - cut up old milk crates was the sort of thing I had in mind, covered in a membrane of some sort.

Having dug down a bit, it seems clear that it is not a real soakaway... just an half-arsed attempt to put a drain hole in the paved area. having got about 10inches deep, I have poured a bucket of water in ... and it is still there (we are on chalk).

We actually had a french drain put in along some of the other edges a few years ago, for unrelated (and probably unnecessary) reasons ... I am wondering about extending it to this edge.

However the guttering downpipes are so close that, assuming they are properly plumbed in, it may be worth actually putting a proper gulley or whatever into those drains.

Thanks for the thoughts & info J^n