Xylem Wastewater (Technical Manual) - Manual (Page 6)

PAGE 6
Wastewater
Goulds Water Technology, Bell & Gossett,
Red Jacket Water Products, CentriPro
The primary function for which the Submersible Sewage Pump is
designed is the handling of sewage and other fluids containing
unscreened nonabrasive solids and wastes. In order to insure
a maximum of efficiency and dependable performance, careful
selection of pump size is necessary. Required pump capacity will
depend upon the number and type of fixtures discharging into
the sump basin, plus the type of facility served. The fundamen-
tals involved in selecting a pump for a Water System can be
applied to selecting a Submersible Sewage Pump. By answer-
ing the three (3) questions concerning capacity, suction, and
discharge conditions we will know what is required of the pump
and be able to select the right pump from the catalog.
1. To simplify the selection of the proper size Submersible Sew-
age Pump, the general rule is to base the pump capacity on
the number of toilets the pump will be serving. This differs
from the selection of the proper pump for a Water System in
that question 1, “Water Needed” is reversed. How much liquid
do we want to dispose of rather than how much do we need?
The following chart will help determine pump capacity:
Sewage Selection Table
for Residential or Commercial Systems
Number of Bathrooms GPM
1 20
2 30
The above selection table takes into consideration other fixtures
which will drain only water into the sewage basin.
Therefore, pump capacity should not be increased for lavatories,
bathtubs, showers, dishwashers, or washing machines. When no
toilets are involved in the facility served, for example, a laundro-
mat, the major fixture discharging waste should be considered.
In this case, the chart should read “Maximum Number of Wash-
ing Machines.”
In areas where drain tile from surrounding lawns or fields enters
the sump, groundwater seepage can be determined as follows:
14 GPM for 1,000 sq. ft. of sandy soil
8 GPM for 1,000 sq. ft. of clay soil
If the calculated groundwater seepage is less than one-fourth
of the pump capacity required based on the number of toilets,
the pump capacity should not be increased. Any seepage over
the allowed one-fourth should be added to the required pump
capacity.
2. Since the pump is submerged in the liquid to be pumped,
there is no suction lift. Question 2 does NOT become a factor
in pump selection.
3. Answering Question 3, discharge conditions is the final step
in selecting a Submersible Sewage Pump. Only the verti-
cal distance between the pump and the highest point in the
discharge piping, plus friction losses in discharge pipe and
fittings affect discharge pressure. (Friction losses can be ob-
tained from the friction table in this Selection Manual.)
Normally service pressure is not a consideration. The total of
the vertical distance, plus the friction losses is the required
discharge head in feet.
SHOWER
TOILET WASHER
VENT SEWER LINE TO UPSTAIRS FIXTURES VENT
HOUSE SEWER LINE TO STREET
RESIDENTIAL SUBMERSIBLE
EJECTOR SYSTEM
DRAIN
PIPE
12'
2" PLASTIC PIPE
AND FITTINGS
Sewage Pump Selection