Harry Bloomfield wrote:
Brian G used his keyboard to write :
Cure, is to dig either a drainage trench to a lower level so the
water runs aways (can then be filled with coarse gravel) or dig an
even deeper trench to about two foot below DPC, backfill with coarse
rubble and use this as a soakaway.

Soakaways with a clay sub soil do not work, unless they penetrate
through the clay level. Faced with the same problem, I dug a trench
around, installing a 'leaky' pipe which led to a drain, all then back
filled with course gravel.

Harry,

Basically as I said above "Cure, is to dig either a drainage trench to *a
lower level* so the water runs aways (can then be filled with coarse
gravel)..." with or without the "leaky" or porous pipe, the water will drain
from a higher to lower level whether in clay soil or not.

As you rightly say, you can get problems with 'level' soakaways on clay
soils, but it can generally be done with a little thought - although I have
come across a few awkward b*****ds in my time. :-)

brian G