Wiktionary
soakaway
n. (context chiefly UK English) A deep hole used for drainage, where rainwater and other wastewater drains directly into the ground, without connection to any mains drainage or sewerage pipes.
Usage examples of "soakaway".
Where the water reached the floor, a crude but effective drain had been put together with modern pipes, which conducted the water into a rubble-filled soakaway hole.
As clearly as could be, she saw the white-tiled shower, its soakaway, and the chrome tap that delivered a mixture of hot and cold water.