Device for preventing water entering a manhole shaft

摘要

A perforated drain cover (2) lies flush with the road surface and covers the top of a shaft (1). A tray (4) with apertures (7) at the sides acts as a sand and leaf trap. Water flows from the sand and leaf trap onto a flat plate (5) with a central aperture (11) with an upstanding flange (12). Air flows through this aperture into a valve chamber (20). The water flows past a tube (18), with an air inlet (17) in each end, and a valve opening (19) in its center, closed by a float (22) on guides (21) when the chamber is full of water. A sieve (16) on the floor (14) of the chamber covers a small drain hole (15).