In article ,
Phil L wrote:

Not really as I can't get it deep enough to be effective, it will need to be
1.3 metres deep and I'm not going two feet into sandstone!

Well, the answer to how large a soakaway has to be in clay is that
it is not a question[*].

Another drawback is that it's going to be less than 5 metres away from a
building, two of them in fact, both houses.

Sad. Provided that you can reach free-draining soil, it doesn't
matter. Our 1930s house had soakaways less than 5 INCHES from
the hous (on 60% sand).
[*] I.e. the predicate is false. To translate, any soakaway on
clay will fill up eventually in the UK, as precipitation exceeds
evaporation even in Essex. My father-in-law dug one 2+ metres
deep and a similar width, and it did, every winter.


Regards,
Nick Maclaren.