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MAJOR COMPONENTS
AND WHAT
THEY DO
Tank and Air Volume
Control
The tank serves
two functions.
It provides
a reservoir
of water,
so that the pump
doesn't
need to start every
time water
is drawn
from a fixture in the house,
and it
maintains
a cushion
of air under
pressure.
When
Captive
Air* Tanks are used, no air volume
con-
trol is necessary.
This tank is precharged
with air at the
factory.
When
a Standard
Tank is used, an air volume
control
adds air to the tank when
it is needed.
See instructions
included
with Air Volume
Control
for details
on instal-
lation and operation.
Pressure
Switch
The pressure
switch
provides
automatic
control.
Model No.
390.2505
Pump Starts At
30 Pounds
Pump Stops At
50 Pounds
When
used
with
a Captive
Air* Tank, the precharge
may need
adjustment.
See the Captive
Air* Tank in-
structions
for details.
Impeller
and Jet
The impeller
of the pump
rotates
with the motor
shaft,
causing
the water to fly out from its rim by centrifugal
force. The rotation
of the impeller
creates
a partial vac-
uum which
pulls in more water.
Part of the water
is di-
verted
back
to the jet where
it passes
through
the
nozzle and venturi,
reinforcing
the vacuum
to draw in
more water
and delivering
it at a high velocity
to the
impeller.
Because
of the shallow
setting,
the partial vacuum
cre-
ated by the pump
is sufficient
to pull water
to the
pump,
therefore,
the jet assembly
is attached
directly
to the pump.
Piping
In The Well
A Shallow well jet pump
can be installed on a dug well,
drilled well or with a driven point. SEARS shallow well jet
pumps have a built-in check valve. In a dug or cased well,
a foot valve and strainer is recommended
and should be
installed 5 to 10 feet below the lowest level to which the
water will drop while pump is operating
(pumping
water
level), See Figure 3, Page 4. Your well driller can furnish
this information.
The strainer should not be too close to
the bottom, or sediment
may clog it. Before installing foot
valve, check to see that it works freely.
When
using a foot valve, a priming
tee and a plug as
shown
in Figure 1, is recommended.
Be sure the total lift from the pumping
water
level to
the pump
does not exceed
20 feet if the pump
is over
the well, or less if the pump
is offset
from the well.
Both figures
arc for sea level - the maximum
lift at
which
the pump
can operate
satisfactorily
decreases
with the elevation
at the approximate
rate of 1 foot per
1,000 feet of elevation.
Thus, if the lift is 17 feet and
your elevation
is 3,000 feet above sea level, you would
then
be pumping
17 plus 3 or 20 feet. This is still sat-
isfactory
for shallow
well pumping.
Horizontal
Piping
From
Well
To Pump
On well point
installations
where
the horizontal
pip-
ing is more
than 25 feet, a check
valve should
be in-
stalled as shown
in Figure 3, Page 4.
When
the pump
is offset more
than
25 feet from the
well, horizontal
piping
should
be increased
in size to
reduce friction
losses. In no case should
the offset pip-
ing be smaller
than the suction
tapping of the pump.
Horizontal
Offset
Piping Sizes
for Shallow Well Jets
1-1/4"
1-1/2"
2"
Up to 25 Ft.
25 to 50 Ft.
50 to 200 Ft.
Discharge
Pipe Sizes
When
the pump
is set a distance
from the house
or
point
of water
use, the discharge
pipe
size should
be
Increased
to reduce
pressure
losses caused
by friction.
1"
1-1/4"
1-1/2"
Up to 25 Ft.
25 to 100 Ft.
t 00 to 600 Ft.
Emergency
Power
In some
areas
and with
some
installations,
an emer-
gency power
supply to guard against power
failure is a
good
idea.
If you install
an engine-generator
set for
emergency
backup
power
for your pump,
supply
the
generator
set manufacturer
with
the nameplate
data
from the pump
motor.
He will then be able to provide
a generator
of the correct
size to power
your pump.
Also, be sure to add the load from any other accessories
(such
as lights) that may be on the same circuit.
and piping
Relief "
Valve
Priming Tee
Figure
I
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