On Aug 2, 4:41*pm, "Phil L" wrote:
IME it's not worth a carrot in terms of draining ground, and certainly
useless as a soakaway, it does have an effect over large areas like farmers
feilds in reducing waterlogging, but far more effective would be 2 milk
crates wrapped in weed membrane and surrounded in 3/4 stone, with a gulley
into the top - a soakaway is just a holding tank, designed to hold flood
water until the surrounding ground can take it away naturally.

Perforated pipe should work fine into a drain.

Perforated pipe into a soakaway needs careful examination of the
ground.
The soakaway needs to be sized according to the rate at which water
can soakaway (volume) versus the area being drained. That means a test-
pit to see if digging down through (say) clay eventually finds a free
draining layer. Milk crates provide a lot of space, the old rubble pit
was more a pond if the area could not drain fast enough :-) The test
used to be dig down in February and watch (time) what happened to the
water.

Linear drainage will handle bulk surface water drainage on clay
somewhat better, Aco and other makes exist.