TM 5-814-2/AFM 88-11, Vol. 2
Figure 5-2. Typical pump-system curves.
For pumps driven by varible speed drives, the storage
5-3.
Wet well design
volume may be small provided pumping rates closely
a General. Wet wells will be constructed at
match the incoming flowrates. The volume required for
pumping stations for the purpose of storing wastewater
the wet well will be computed with the following formula:
flows prior to pump operation. The storage volume
required depends upon the method of pump operation,
V = tq/4
i.e., whether pumps are constant, adjustable or variable
where
speed.
In addition to providing adequate storage
V=
required volume in gallons
volume, wet wells will be designed to (1) allow for proper
between start and stop elevations
pump and level controls, (2) maintain sufficient
for a single pump, or a single
submergence of the pump suction inlet, (3) prevent
speed step increase for adjustable
excessive deposition of solids, and (4) provide
or variable speed operation
ventilation of incoming sewer gases. In smaller stations,
bar racks or comminuting devices may be installed
within the wet well in order to reduce costs. Overflows
from wet wells are prohibited in all cases.
b Storage volume. If pumps are of constant or
adjustable speed type, the wet well volume must be
large enough to prevent short cycling of pump motors.
5-5
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