TM 11-6780-225-35
ing operation all valves except P1 are closed. Water
ment of the sink under gravity pressure, to prime the
flows from the small compartment of the sink through the
water pump and fill the water tank. When the water tank
drain line into the water pump, instead of flowing out of
is full, water will flow from valve S8. The water system
the water drain through valve D1, as during normal
now functions as in c above.
operation (e below). With valves P1 and S2 closed,
e. Water Drainage. Normal water drainage of the water
valves S1 and S3 open, and the water pump operating,
system is described in (1) below. Drainage of the water
air is evacuated from the line leading to the water pump
tank only is described in (2) below, and complete
causing water to flow into the water pump by suction.
drainage of the water system is described in (3) below.
From the water pump, water is forced under pressure
through the check valve and into the pressure regulator,
operation all drain valves, except D1, are closed. Waste
which, if required, will reduce the water pressure to a
water is forced under gravity pressure out of the water
maximum of 40 psi. The check valve allows waterflow in
drain connection and into the water drain hose.
only one direction, and prevents any backflow of water to
the water pump. Water is also forced under pressure to
always remain open during this operation to allow air to
the pressure relief valve (adjacent to S2) and to the
replace the water that is pumped from the water tank.
pressure switch. In case of a malfunction in the system,
With valve D2 closed and S9 open, water flows from the
the pressure relief valve will return the water to the water
water tank to prime the water pump under gravity
pump when a pressure of 90 psi is reached. The
pressure. With valve S2 open and the water pump
pressure at the water pump is sensed by the pressure
operating. water is drawn from the water tank by suction
switch which will allow current flow to the water pump
and forced under pressure out of the water inlet. Valves
motor when the pressure at the water pump falls below
S1 and S3 must remain closed to prevent water from
20 psi, and to stop current flow to the water pump motor
reentering the water system under pressure.
(3) Complete water system drainage. Complete
when the pressure at the water pump exceeds 40 psi.
From the pressure regulator the function of the water
drainage of the water system is accomplished by
system is the same as in a above, when the water flows
opening all valves in the water system, and allowing the
from the pressure regulator.
water to flow to the outside of the darkroom under gravity
c. Darkroom Water Tank Water Source. When
pressure. Water from the large and small compartments
using the water tank as a water source, valve SS must
of the sink will flow both through valve D1 and out of the
always remain open to allow air to replace the water that
water drain connection, and through valve D3 and out of
is pumped from the water tank. The water tank may be
the floor drain manifold. Water in the lines supplying
filled either from a water source under pressure (a
valves S4, S5, S6, and S7, and water from the hot water
above), or from water from a lake or stream (b above).
tank will flow through valve D4 and out of the floor drain
With the water tank full and valve S9 open, the water
manifold. Water in the lines from the outlet pressure
pump is primed by water flowing from the water tank
indicator and the flow indicator will also flow through
under gravity pressure. Once primed, the water pump
valve D4 and out of the floor drain manifold. Any water
will cycle on and off continuously since no pressure is
in the lines between the pressure vacuum indicator and
built up in the water tank due to water being drawn by
the level indicator will be drained onto the compartment
suction through valve S9. From the water pump, the
floor through valve D13. Water in the lines from valves
water is forced into the pressure regulator. From the
S3 and S9, and water from the water tank will flow
pressure regulator, the function of the water system is
through valve D2 and out of the floor drain manifold.
the same as in a above, when the water flows from the
Water from the strainer flows through valve D6 and onto
pressure regulator.
the compartment floor. Water in the lines from the water
d. Snow as a Water Source. With the small
inlet, valves P1, S1, and S2, the filter, inlet pressure
compartment of the sink filled with snow, the immersion
indicator, pressure switch, pressure relief valve, and
heater is connected to circuit 4 and placed into the snow
pressure regulator will flow into the water pump, out of
until the snow has melted. Valve S8 must always remain
valve D7 and onto the compartment floor. Water from
open as in c above. With valves P1 and S9 open, the
the check valve flows out of the check valve drain
water from the melted snow flows from the drain of the
petcock and onto
small compart
2-6
