MIL-HDBK-1164
Table 36
Maintenance Checklist for Gravity Filtration Equipment
Frequency (1),
Inspection
Action
(2)
Filter media
Inspect surface for unevenness, sink
M
holes, cracks, algae, mud balls or
slime.
Dig out sand and gravel at craters of
V
appreciable size.
Locate and repair underdrain system
V
breaks.
Chlorinate to kill algae growths.
Q
SA
Probe for hard spots and uneven
gravel layers; if present, treat filter with
acid.
Check wash water rise rate and sand
SA
expansion during backwashing.
A
Check sand condition for grain size
growth; sample sand, determine weight
loss on acid digestion, and run sieve
test; acid-treat if necessary, or replace
sand, if necessary.
Gravel
Check elevation of gravel surface.
M
SA
Examine gravel for encrustation,
cementation, alum penetration, or mud
balls; if necessary, remove, clean, and
re-lay gravel.
Underdrain system
Remove sand from an area 10 feet
A
square (1 sq m) and inspect an area of
gravel 2 feet square (0.2 sq m) or
larger. If underdrains are deteriorated,
remove all sand and gravel, repair
underdrains, and replace gravel and
sand.
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