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Well Wizard®
Installation and Operation Manual
Rev. A 2-1-2018
Bladder Pump Operation in Low-Submergence Applications
Pump submergence is defined as the height of the static water column above the top
of the pump. In wells in which this water column height is 5 feet or less, the pump is
considered to be in a low-submergence application.
QED sampling bladder pumps fill by hydrostatic pressure. As the inside of the pump’s
bladder fills with water, the bladder expands. This filling and expanding of the bladder
is referred to as the “refill” half of the pump cycle. When air pressure is applied to the
outside of the bladder, the bladder is squeezed, forcing the water up the discharge
tubing. This is referred to as the “discharge” half of the pump cycle.
In low-submergence applications, there is less water pressure available to expand the
bladder during the refill.
This can result in a smaller volume of water being pumped with each pump cycle
because the bladder may not fully expand.
As a result of the lower volume per cycle, more time will be required to bring the
water to the surface. An easy way to verify that the pump is working, prior to the
water reaching the surface, is to submerge the pump’s discharge tubing in a beaker
of water. Each time the pump goes into discharge, air in the discharge tubing, which
is displaced as the water level in the tubing rises, can be seen as air bubbles coming
from the end of the tubing. To optimize the pumping rate, the refill time should be
set long enough to achieve the maximum volume of air bubbles on each pump cycle,
and the discharge time should be set long enough to ensure that the air has stopped
bubbling out of the tube before the pump controller switches back into refill.
In low submergence wells,
it is critical that the air pressure driving the pump not
be more than 10-15psi higher than the minimum requirement of 0.42psi per foot
of pump depth.
Higher pressures than this can cause the bladder to be squeezed too
tightly during discharge, a condition which can prevent the bladder from expanding
during refill. To avoid this condition in deeper wells, it is suggested that the air
pressure applied to the pump be gradually increased as the water level in the pump’s
discharge tubing rises. It is recommended that the air pressure be set at 15psi
initially, and slowly increased in increments of 10psi as needed until the water reaches
the surface. Submerging the end of the discharge tubing under water as described
above will verify whether the air pressure is set high enough.
Bladder Pump Operation In Low-Submergence
