1 March 1997
Engineering Manual provides engineering data to be used in designing clay pipe sewers.
m. Special materials. In designing sewer systems for military industrial installations, pipe
and appurtenances made of materials which are subject to attack by acids, alkalies or high
temperature, highly corrosive industrial type wastewaters, will not be included in the
specifications. The designer will carefully evaluate the particular wastes involved, and will
indicate in the specifications the types, concentrations, and temperatures of the various waste
materials to be encountered. Conditions seldom exist at military installations requiring discharge
of acids, or other type wastes, in such concentrations that vitrified clay pipe would not be
suitable. However, there may be situations where extremely corrosive wastes preclude the use
of V.C. or other pipe materials covered in this manual. For these occasions, special pipe
materials, linings, or coatings will be selected using manufacturers recommendations, and any
other applicable publications. Laboratory certification of pipe or material performance may be
required in cases of unusual wastes.
n. Other Considerations. Solvent cement joints minimize the possibility of poor joint
construction, and greatly reduce groundwater infiltration.
8-2. VALVES AND APPURTENANCES. The use of valves in wastewater pumping can be
divided into the following categories:
a. Isolation or shutoff valves. Where the need to isolate pumps or part of the piping system
occurs, manually operated shutoff valves will be used. Gate valves or butterfly valves generally
serve as shutoff valves, however ball valves or plug valves may also be used. Shutoff valves are
required on the suction and discharge sides of all pumps.
b. Surge control valves. To protect pumps and piping from surges caused by pump
shutdown or power failure, gravity operated swing check or ball check valves, or automatically
operated cone, plug, ball or butterfly valves will be installed in the pump discharge line. The
operation of surge control valves is discussed in paragraph 7-7.
c. Blowoff valves. A valve outlet installed at the low point in a force main, and arranged to
drain or flush the pipeline, is termed a blowoff. Normally, blowoffs will be required only on long
depressed sections of force main, or where an accumulationof solids is likely to occur. Blowoff
connections will be in-stalled in manholes or valve structures, and will be protectedagainst
freezing. A means of discharging to a suitable locationmaterials flushed from the system will be
provided. The pipesize of the outlet connection should coincide with the size of the force main.
d. Air valves. Air valves will be installed at high points in force mains for the purpose of
admitting and releasing air. When the pipeline is taken out of service for draining, flushing and
filling operations, a manually operated valve will be adequate. However, where air pockets or
pressures less than atmospheric are likely to occur with the pipeline in service and under
pressure, automatic air release and/or air vacuum valves will be used. Manual valves can also
be used with the pipeline under pressure by leaving the valve partially open. Automatic valves
are not recommended due to maintenance problems, and should be used only where absolutely
required. Automatic valves will be of a type specially designed for sewage, and will be provided
with backflushing connections. All valves will be installed in a manhole or valve structure with
adequate drainage and protection against freezing.