PC Ring Soakaways are commonly used for sites of smaller impermeable areas (generally less than 500 square metres).
Precast concrete rings are commonly available in sizes 900, 1050, 1200, 1350,1500, 1800, 2100, 2400 and 2700mm in diameter. This variety of soakaway is produced with slots in the outer wall to provide easy filtration of water to the surrounding soil.
The design of this type of soakaway is very similar to the trench type arrangement and uses the same formulas to balance the inflow and outflow. The half emptying time is also calculated in the same way.