HILL. 157

separated by a deep, central trough which serves the ible
At foi the settled water and an outlet for the wash w
most interesting feature of the filters is the strainer .
diameter cast-iron pipes are used for this (see Fi 7).
,boyv the floor bI lugs cast on the bottom of the pi hus
ly a continuous horizontal orifice, -in. wide on bot
all hples in the top at each of the pipes provide f'the
ed ar.
of gi avel, varying in.size from 2j in. to A in. in si*sind
.n d pth, cover the lateral pipes. Thirty inches of nd,


















 FIG. 28. WASH WATER TANK.

e size of approximately 0.4 millimeter and a uniforO*ty
oximately 1.6, surmount the gravel.
ter troughs are of concrete having half-round upper ef es.
if Tennessee marble with slate tops are set directly in bnt
11 filter valves 4re hydraulically operated and conti ed
Stables, on which are placed the valve position indicprs
he rate of flow, loss of head, and recording gages. 1
operating gallery is located the pipe gallery. Ac to
by means of two ornamental iron spiral stairways m'
utsile entrances at each end. The pipe gallery isi r-
lobst ucted passageways and freedom from a large a t
,ing. The wash-water pipe is suspended from the c g

er, wch is stored in a 100 000-gal. elevated tank (FigB),
eansf a Rose pressure-reducing valve.