Water-level overflow in a shaft of a spring

In order to maintain a maximum water level (7) in a shaft (1), use is made of an overflow pipe (8) which is connected to an emptying line (9) which leads into the open. The upper free end of the overflow pipe (8) is provided with a device which is intended to prevent the penetration of small animals, harmful gases and unpleasant odours into the shaft and into the water located in the shaft. This device comprises, for example, a trough (11), enclosing the mouth of the overflow pipe (8), and a bell (12) which dips into the trough (11) via the overflow pipe (8). This bell siphon may be provided with a handle (13). The water, which flows in through a supply line (5) and flows out through a discharge line (6), thus remains clean. At ground level (3) the shaft (1) is closed by means of a well cover (2) which may be provided with a lock.