Elite 799 User Manual page 6

To regulate air volume using an air control valve with multiple
outlets, it is recommended to have the last valve available to release
excess air pressure build up (see BACK PRESSURE). In regulating
the air pressure, it is best to work from the valve farthest from the
input of the air valve. Remember to have the last valve completely
closed so as not to lose any air pressure. Proceed to make
adjustments on the remaining valves. Once the adjustments are
complete slowly open the last valve to the point where no loss of air
output is noticed from the items controlled by the other valves. To
achieve and maintain an equal balance of air pressure to the
accessories in the aquarium, further adjustments of the air valve
may be required depending on the items powered by the air pump.
Note: If the first valve on the air control assembly is fully
opened, air volume to the remaining outlets will be reduced.
To alleviate excess air pressure or overproduction of air, it is
recommended to open the last valve every 2 weeks, or when
required. In doing this, you will increase the life of the pump
and diaphragms by preventing premature wear.
BACK PRESSURE
Back pressure is the buildup of pressure on the diaphragm due