Surface water control for new/replacement patio

[Ouch77]

I'm in the process of replacing some horrible decking at the end of my garden with a patio. At the same time I'll also be replacing a badly laid patio/path at the house end with more of the same.

Surface water drainage is currently non-existant, the decking is porous, and the existing patio is just slabs on mud.

The house (mid 60's) has combined drainage for surface and soil, but for practicality sake as well as environmental I'd like to use soakaways instead.

The patio areas are 27 and 25sq m (top and bottom). The proportions and location of the patios are such that allowing them to surface run-off onto the intervening lawn would probably soak the lawn too much.

I was thinking of burying several Suds type crates in a line between the two patios, and draining one into each end - 6 crates would give me 1.2 cubic metres which I estimate to be adequate in usual circumstances. The surface water capture would be via linear drain installed on each patio.

However, I hear that soakaways are less effective on clay soil, the soil around my house does have a clay component, though we've never experienced any surface flooding or water-logging in the past 4 years. The land is relatively flat with a slight fall from back to front.

Am I asking for trouble using soakaways in this scenario? Would it also be a problem if the soakaway was to one side of the garden, so adjacent to a neighbours land?

Another option would be to install a land drain beneath the lawn in place of the soakaway - is there any guidance as to what sort of area or linear meterage would be required to adequately cope with the runoff? Could I use both a collector and a dispersal arrangement to even out the water content caused by surface runoff onto the lawn - thus negating the need for linear drain channel?

Thoughts and advice welcome..

 

[WabbitPoo]

You are right that soakaways can be useless in clay...the best thing to do is dig a trial hole to see if you can dig down past the clay - then fill with water to check it disappears.

The general problem with soakaways can be that you end up draining the adjacent gardens, especially if yours is lower than theirs. That may not be what they, or you, want.

Why don't you want to drain the water to the drainage system your council has provided for you (and for which you pay for the priveledge?)

 

[r896neo]

If you have room for a soakaway, which must be 5m from and building, you must use that option before before discharging to a drain.

There is lots of good advice on the paving expert . com website regarding trial pits and perculation tests

 

[Ouch77]

If you have room for a soakaway, which must be 5m from and building, you must use that option before before discharging to a drain.

There is lots of good advice on the paving expert . com website regarding trial pits and perculation tests

Yup, been hitting AJ McCormacks website pretty hard recently

I think I'll try the trial hole approach, the boundary that's the closest to the proposed soakaway site is lower, so in theory it'll have less an effect on the neighbours garden - which is mostly patio anyway.

Do we think the land-drain idea is a non starter then?

 

[r896neo]

The patios are big enough to warrant a drain of some sort but if you have the right gradients you could just fall it to a lawn.

Sometimes a fin drain along the edge of the lawn/patio is worthwhile to deal with the initial surge of rain.

Of course if your lawn is already boggy and holds water then this is a no go.

 

[Ouch77]

My worry with a drain alongside the lawn would be of it collecting too much in the way of grass clippings. I'd probably try to fall away from the lawn, especially at the top/far end of the garden, and put a linear drain on the boundary.

 

[Ouch77]

Update/thread resurrection...

Been doing a bit of digging (literally and online) and have come to the following conclusions:

Top patio can fall towards the lawn with no ill effect. A land drain network under the lawn will help distribute the water within the lawn area to prevent over saturation.

Bottom patio needs to be lower than the lawn by about 150mm due to the height of the damp-course of the conservatory it is adjacent to. Thus falling towards the lawn will be a bit hard.

Solution, fall towards the house and collect runoff in a linear drain that then connects to the land drain network mentioned above.

Simples

Now to find the parts and install it...

I can find loads of different linear drain systems online, but I'm having trouble finding fittings that will connect to it -most linear drain systems look as though they want to connect to 3" pipework (fernco for example).

But I can't find any 3" fittings on the various websites - I need a right-angle bend (coming from the bottom of the gulley) and about a 3m length to connect to the dispersal land drain.

Any suggestions anyone?

 

[r896neo]

Most aco's comes with an accessory pack which allows for a punch out to be taken out of the base and a connector fitted to push fit into a standard 4'' pipe collar