Soakaways ~ provide a means for collecting and controlling the
seapage of rainwater into surrounding granular subsoils. They are
not suitable in clay subsoils. Siting is on land at least level and
preferably lower than adjacent buildings and no closer than 5 m to
a building. Concentration of a large volume of water any closer
could undermine the foundations. The simplest soakaway is a
rubble filled pit, which is normally adequate to serve a dwelling or
other small building. Where several buildings share a soakaway, the
pit should be lined with precast perforated concrete rings and
surrounded in free-draining material.BRE Digest 365 provides capacity calculations based on
percolation tests. The following empirical formula will prove
adequate for most situations:-C=AR 3
where: C = capacity (m^3 )
A = area on plan to be drained (m^2 )
R = rainfall (m/h)e.g. roof plan area 60 m^2 and rainfall of 50 mm/h (0„05 m/h)C=^60 ¾ 3 0„05= 1„0 m^3 (below invert of discharge pipe)
Ref. BRE Digest 365: Soakaways.Rainwater Drainage---Soakaways