Where the drainage system cannot drain by gravity to the sewer, an automatic pump or ejector can be used to discharge the soil and waste. The cover for the pump should be tightly sealed (gas-tight). Sumps, other than pneumatic ejectors, should be vented with a minimum 1-1/4-inch diameter vent pipe. Pumps use mechanical methods to discharge, and pneumatic ejectors use air pressure. Grinder pumps and ejectors pulverize solids to a near-liquid state and pump the slurry to the drainage system.
The capacity of the sump should not exceed one-half of a day’s (12 hours') discharge load from the piping system connected to the sump under normal use. The retention period should be short to prevent the pump from acting like a septic tank. The minimum capacity of the sump should be such that the pump operates for at least 15 seconds per pumping cycle to prevent short-cycling and overuse of the equipment. The level of the effluent in the pit should not rise within 2 inches (51 mm) of the gravity drainage pipe entering the pit.
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