When the house drain is run overhead, it is clear that the cellar and subsoil drainage cannot be disposed of by gravity in the ordinary manner, as just described. The device used in raising the subsoil water is the automatic cellar drainer, and it is also used for removing water from excavations, wheel pits, or other depressions where water accumulates.
The drainer is placed in a pit or manhole below the cellar bottom, into which the drainage to be raised is discharged. As soon as the water collects to the depth of about a foot in the pit, the drainer opens and discharges the water.
As the water rises in the pit, a float attached to the drainer is gradually raised, and when a certain level is reached, the lever to which it is attached opens the valve wide, allowing water or steam-pressure to pass through the drainer, and thereby drawing or sucking the water from the pit into the discharge pipe.
The drainer is generally operated by water pressure, this connection being made to any supply pipe. The water passes under full pressure through the drainer point or jet, thus creating the necessary suction to draw the water out. When the water has been removed from the pit, the valve instantly closes, and the drainer again becomes inactive.
The water in passing through the jet of the drainer creates a vacuum, this vacuum being the means of producing the necessary suction. The discharge pipe from the drainer should empty the water of the pit, and the pressure water used in operating the apparatus, into a sink or pan located above the house drain, into which the drainage may then flow by gravity. The sink or pan should be trapped and vented in the same manner as any other fixture.
In general, the cellar drainer requires a water pressure of four or five pounds for each foot through which the water is to be raised vertically. The cellar drainer is not adapted to raising water over 12 ft. usually, and many of them lose much of their efficiency after passing 8 ft.
The drainer may be located in an underground box or barrel. Cellar drainers are capable of raising from 250 to 1,200 gallons of water per hour.
The sizes of supply pipe generally used are 1/2 in. for small sizes, 3/4 in. for medium sizes, and 1 in. and larger for large sizes.