Soakaway

[sPoNiX]

How big should I dig a soakaway assuming that it is fed from an 8'x10' flat roof and the soil is clay?

sPoNiX

[Toby]

7.5m2 roof > 0.125m3 chamber 5m away from any building but states: "Note that this is the storage volume required between the dry base or water table level of the soakaway, and the invert (inlet) level of the incoming drainage pipe, and assumes that the chamber is empty, not filled with old bricks, lumps of concrete or gravel, etc., as is often found in older soakaways. If the chamber were to be filled with, say, a gravel, this would significantly reduce the storage volume, requiring a much bigger chamber to be constructed."

[Stuart]

Enormous!

If you have good quality clay you will just end up with a pond!

[Angus C]

Water butt?

[John Schmitt]

A small roof, 10x12 m, yields 120 litres of water per millimetre of downfall. The driest places in the UK mainland seem to have recieved more than twice this yesterday, and the wettest over 32 mm. That is nearly 4 cubic metres of water to deal with. It rather looks like most of the mainland can look forward to similar precipitation until at least Friday, which is a lot of barrels of water.

John Schmitt

[sPoNiX]

That is something worth considering..

The problem I have is that no drain is accessible as it is a mid-terraced property with downpipes on neigbouring properties and 5 metres will be outside the property boundary!

sPoNiX

[Michael Mcneil]

Can't you nail it to the washing machine waste outlet when no-one is looking?

[Ian Stirling]

A really big fountain, into next-doors garden?

[sPoNiX]

I must admit they do have a piece of timber decking adjoining our garden and I had thought of feeding a pipe underneath..

sPoNiX

[Harry Bloomfield]

on 19/04/2004, sPoNiX supposed :

If it is a solid layer of clay as a subsoil, as soak away will never work because clay is impervious to water....

What I did, was use a large water butt as a buffer, then added an outlet 1/3 the way up. To the outlet I fitted a long length of garden hose which drained the water to a more suitable location. Bit of a botch I know, but the nearest drain was 40 metres away and it was only for my summerhouse. The roof area was much bigger than yours.

[T i m]

I'm slightly confused by this (well not *just* this ).

You have a 30' square lawn and build a 6' square greenhouse / shed in the middle of it.

You are then supposed to dig a soakaway (assuming you don't have access to a surface water drain) to run the water collected from the roof to within 3' of where it would have gone had it just just fallen on the ground anyway? Wouldn't the water 'soak' sideways under the building anyway?

As mentioned you can add a water butt as a 'buffer' (if you have no use for the stored water it might only buy you a couple of days) and then what? Where does the 'surplus' go?

What if you laid an irrigation system uder the greenhouse / shed so that the roof water simply went where it would have gone in the first place?

Just thinking out loud ... ;-)

All the best ..

T i m