EP 1110-1-27
27 Jan 00
Chapter 9
Suggested Maintenance (Minimum and Optimum)
The following paragraphs list recommended maintenance practices, intervals, and evaluation processes.
They are adapted from more in-depth discussions elsewhere (e.g., Borch, Smith, and Noble 1993;
Howsam, Misstears, and Jones 1995; Powers 1992; Smith 1995; ADITC 1997; NGWA 1998) and project
experience.
9-1 Design Aspects
A variety of design considerations can serve to prevent or slow well system deterioration, and facilitate
maintenance and rehabilitation in the future. In many cases, the improvements cost little or no more than
inferior designs and materials initially, and save money in life-cycle costs.
well components and limit recurrence of preventable problems, making the success of maintenance
actions more likely. EM 1110-1-4008 provides information on material compatibility. Specific to well
equipment, polyvinyl chloride (PVC) casing, for example, is corrosion-resistant and suitable for most
HTRW applications. Alternative metal casings are available where plastic or fiberglass casings are not
suitable (Smith 1995; NGWA 1998). Notable product developments (approaching 20 years in service)
include the widespread availability of all-stainless-steel and stainless-and-plastic pumps, high-quality
rigid plastic pump discharge (drop) pipe with twist-on-twist-off connections, and flexible discharge hose
(specifically designed for well pump use) composed of reliable, high-strength, corrosion-resistant material
that permits easy pump service. Relatively smooth pump interior surfaces and corrosion resistance are
showing increasing intervals between pump service events.
b. Other pump selection considerations. Pump motor and discharge-end product lines can seem to
have a remarkable sameness in a competitive market. On the other hand, pumps may be marketed for
"environmental duty" which may not be superior to other products for aggressive ground water pumping
applications. Some considerations:
(1) Pump end material selection.
(a) A material designation of "stainless steel" includes a range of corrosion-resisting alloys. Some
do well in anaerobic environments typical of high-organic-carbon water (e.g., Type 316 and better), and
some do not (Type 304). The alloy should be selected to be compatible with the service environment.
(b) Welding and stamping alter the corrosion-resisting characteristics of stainless steel alloys so
that the manufactured product may not match the resistance of the unaltered alloy. In some cases, a cast
stainless bowl selection may be superior.
(c) While versatile, stainless steel may not suit every situation. In some high-chloride, bio-
corrosive environments, only high-silicon bronze or plastics may provide suitable service life. At high
temperature or high radiological activity , some plastics degrade at unacceptable rates. In addition to bowl
and impeller materials, selections of bearing materials and designs are factors in selection.
(2) Pump end hydraulic efficiency. Higher efficiency pump ends are recommended. Pump
impeller-bowl designs and numbers of stages should be matched to the operating head conditions.
9-1
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