Current through Register Vol. 41, No. 3, September 23, 2024
A. General. Wet
well-dry well pump stations shall meet the applicable requirements for both
types of systems. Both wet and dry wells shall be separated to prevent leakage
of gas into the dry well. A separate sump pump or suitable means shall be
provided in the dry well to remove leakage or drainage, with the discharge
above the high water level of the wet well. Vacuum ejectors connected to a
potable water supply will not be approved. All floor and walkway surfaces shall
have an adequate slope to a point of drainage. Drainage shall be unobstructed
by conduit, piping, etc., installed on the dry well floor.
B. Suction lift. Suction lift pump
installations shall be designed to meet the applicable requirements of this
chapter.
1. The capacity of suction lift pump
stations shall be limited by the net positive suction head and specific speed
requirements as stated on the manufacturer's pump curve under the most severe
operating conditions.
2. All
suction lift pumps shall be provided with an air relief line on the pump
discharge piping. This line shall be located at the maximum elevation between
the pump discharge flange and the discharge check valve to ensure the maximum
bleed-off of entrapped air. Air relief piping shall have a minimum diameter
adequate to purge air during priming. The use of 90° elbows in air relief
piping should be avoided. A separate air relief line shall be provided for each
pump discharge. The air relief line shall terminate in the wet well or suitable
sump and open to the atmosphere.
3.
Valving to prevent recycle of flow to the wet well should be provided on all
relief lines. The air relief valves shall be located as close as practical to
the discharge side of the pump. Automatic operating air relief valves may be
used if the design of the particular valve is such that the valve will fail in
the open position under varying head conditions. Unvalved air relief piping may
lead to air entrainment in the sewage and will materially affect pump
efficiency and capacity. Air entrainment shall be considered accordingly by the
design consultant.
4. All pumps,
connections, shut-off valves, and check valves shall be located in a separate
vault either above or outside of the wet well, allowing accessibility to both
the wet well and pump/valve vault for inspection, maintenance, etc.
5. Access to the wet well shall not be
through a sealed vault. The dry well shall have a gas-tight seal when mounted
directly above the wet well.
C. Submersible. Submersible pump station
installations shall be designed to meet the applicable requirements of this
chapter.
1. Submersible pumps shall be
provided with equipment for disconnecting, removal, and reconnection of the
pump without requiring personnel to enter the wet well.
2. Owners of submersible pumping facilities
shall provide a hoist and accessories for removing the pumps from the wet
well.
3. Electrical controls shall
be located in a suitable housing for protection against weather and
vandalism.
4. The shut-off valve
and check valve on the discharge lines of pumps operating at flows greater than
25 gpm shall be located in a separate vault outside of the wet well allowing
accessibility for inspection and maintenance.
D. Pneumatic ejectors. Pneumatic ejector
stations shall be designed to meet the applicable requirements of this chapter.
Pneumatic ejectors should not be directly connected to force mains. The ejector
design features should include:
1. Ejector
pots shall be vented to the atmosphere in such a manner as to prevent nuisance
conditions.
2. Duplicate
compressors shall be provided.
3.
Pneumatic ejectors may utilize either stored or direct air systems. If a stored
air system is utilized, the air storage chamber shall not enclose any piping,
valves, or working parts.
4.
Duplicate receiver pots shall be provided. The units shall be alternated in
operation.
E. Grinder.
Grinder pump installations shall be designed to meet the applicable
requirements of this chapter.
1. Maintenance
and operation service arrangements shall be identified to the division.
Acceptable service arrangements shall include:
a. Right of access.
b. Adequate spare parts, spare units and
service tools.
2. A
single pumping unit for a single home or equivalent flow is acceptable, but the
wet well capacity for a single family residence should be a minimum of 60
gallons.
3. Duplex pumping units
shall be provided where two houses or equivalent flow are served by a single
installation. The wet well or holding tank capacity shall be twice the
requirements for a single house.
4.
The alarm system should provide notice to residents of pump failure, including
excessive high liquid levels. The alarm system should alert the operating staff
of the location of pump failure.
5.
Pumping equipment shall be capable of delivering flows at the design pressure
of the sewer system. Cutter blades shall be driven with a minimum motor size of
two horsepower, unless performance data, evaluated by the department, verifies
that a smaller motor is suitable.
F. Septic tank effluent pump. Septic Tank
Effluent Pumps (STEP) may be located within the effluent end of a single tank
or within a separate vault external from the septic tank. The design for STEP
facilities is described in published literature, such as the USEPA Technology
Transfer Manual "Alternative Wastewater Collection Systems" (EPA/625/1-91/024),
which may be used as a reference.
Statutory Authority
§ 62.1-44.19 of the Code of Virginia.
