GRINDER
PUMP PRESSURE SEWER SYSTEM
DESCRIPTION
Uwharrie Point is served by a grinder pump pressure
sewer system. Grinder pumps utilize
grinder blades fitted on a submersible pump to macerate waste to a slurry which
can be pumped through a small diameter pipe, generally referred to as pressure
sewer. Grinder pump pressure sewer
systems have been employed for more than 30 years in the United States as a
practical and economical alternative to conventional gravity sewers.
Grinder pump pressure sewer systems are comprised of
multiple grinder pumps connected to a network of small diameter PVC pipe
through which wastewater is pumped to a common discharge point, such as a
treatment plant.
Each home in Uwharrie Point has a grinder pump unit
which receives wastewater from the residence, then pumps it through the pressure
sewer system to Uwharrie Point Wastewater Treatment Plant.
The primary components of the grinder pump unit are
the pump basin, grinder, submersible pump, pump motor, lift out rail system,
control box, and alarm system. Typical
grinder pump arrangements are illustrated in the attached exhibits.
OPERATION
Wastewater flows by gravity from the house to the pump
basin through the 4-inch diameter sewer hose connection line. The pump basin acts as a holding receptacle
for wastewater generated by the household and has sufficient storage capacity
to allow the pump to be out of service for 24 hours.
When wastewater reaches a specified level in the
basin, a float control switch activates the pump, and the pump runs until the
level in the basin drops to the “pump off” float control switch.
Solids normally found in domestic wastewater are
shredded by the grinder to form a liquid/solid slurry, which is pumped by the
submersible pump to the pressure sewer in the street, and eventually to the
wastewater treatment plant.
The control box contains all of the electrical control
elements for the grinder pump unit. The
grinder pump unit operates on single-phase power, with a 230/115 volt, 3 wire
neutral system. The control circuit is
115 volts.
The lift out rail system allows the pump to be easily
removed or installed for service by simply pulling it up the rail with the lift
chain.
If the pump fails to operate for any reason, the alarm
system will alert the homeowner to call for service. The alarm system includes visual (flashing red light) and audible
(horn) alarms.
MAINTENANCE
Grinder pump systems have a record of being highly
reliable. Data gathered by the
Wastewater Pollution Control Federation indicate that the mean time between
service calls on an individual unit is typically about 5 to 10 years.
Preventative maintenance for the grinder pump unit
should include pump well cleaning and an annual inspection of the equipment,
particularly the pump, float switches, and electrical panel. Any
problems with the grinder pump system should be reported to your plumber. Handy Sanitary District is not responsible
for problems with individual systems on individual lots.
ENERGY
CONSUMPTION
The grinder pump unit consumes very little
energy. For a typical household, the
pump will operate approximately 20 minutes each day; thus a two horsepower pump
will, on average, consume about 180 kilowatt hours per year. Assuming an electric rate of $0.10 per
kilowatt-hour, the annual energy cost of for running the pump would be about
$18.00.
INSTALLATION
The developer has installed individual house
connections to the pressure sewer system to just beyond the valve box at the
street right-of-way. The homeowner is
responsible for connection to the existing line and installation of the grinder
pump unit and the individual schedule 80 PVC pump line from the grinder pump to
the valve box.
Basin
The basin shall be 48” diameter by 60” deep and shall
be molded of fiberglass reinforced polyester resin.
The basin cover shall be of steel coated with high
temperature bake epoxy resin structural plastic, or fiberglass as recommended
by the manufacturer,
Antifloatation Base
Each basin shall have a minimum of 44.3 cubic feet of
concrete poured at its base and attached to the basin in such a way to prevent
floatation of the basin.
Discharge Piping
Discharge piping shall be 1 ½” diameter schedule 80
PVC. There shall be a 1 ½” ball valve
installed in a valve box prior to the right-of-way to isolate the discharge
pipe and grinder pump from the public sewer system.
Shop Drawing Submittal and Inspection
Installation of the grinder pump unit and discharge
piping must be inspected and approved by the County Building Inspector. No individual grinder pump unit shall be
connected to the Handy Wastewater Treatment System until approved and the
installation has passed inspection.
MANUFACTURERS
Three of the largest manufacturers of grinder pumps
have been selected to supply grinder pump units at Uwharrie Point. Each homeowner is free to select the
specified pump from any of the three manufacturers.
The three pump manufacturers and their sales
representatives are as follows:
AURORA-HYDROMATIC
Model SPG200M-2-2,
3450 RPM,
2
HP, 230V, 1 phase, w/5” impeller
Sales
Representative: Mechanical
Equipment Company
Post
Office Box 689
Matthews,
North Carolina 28106
(704)
847-2100
MYERS
Model: WGL-20,
3450 RPM
2
HP, 230V, 1 phase, 5 ½” impeller
Sales
Representative: Pump and
Lighting Company
Post
Office Box 2504
Hickory,
North Carolina 28601
(704)
324-9705
PEABODY BARNES
Model: SGV202L,
3450 RPM
2
HP, 230V, 1 phase
Sales
Representative: Pumps,
Parts & Service, Inc.
Post
Office Box 7788
Charlotte,
North Carolina 28241
(704)
588-6250
It is important that the homeowner purchases the
particular pump model specified in the brand he or she selects. The pump models listed above have been
selected in each brand specifically for their operating characteristics as
applied to Uwharrie Point pressure sewer system.