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| 866 Challenger Series
www.natvac.com | 800.253.5500
Adjusting Ballast Valve Opening Level
The following tools will be required to adjust the ballast valve
opening level:
- 7/32” hex drive
- 1/4” hex drive
- Flat head screwdriver
• Using the 7/32” hex drive, remove the boss plug from the
cover of the ballast valve.
• Using the 1/4” hex drive, remove the locking jam nut.
• The ballast valve opening adjustment screw lies under the
locking jam nut�
• Remove the ballast air filter from the top of the ballast valve.
• Run pump to desired ballast opening vacuum level
(recommend 12” Hg).
• If ballast is not open (and should be), turn adjustment screw CCW
slowly with flat-head screwdriver until air just begins to flow.
• If ballast opens before desired vacuum has been reached,
turn adjustment screw CW slowly with flat-head screwdriver until
air is just flowing.
• Place thumb over adjustment hole and ensure opening
level is accurate.
*Without the boss plug, vacuum chamber is not sealed, thus opening level
may vary slightly.
• If adjustment holds accurate, replace locking jam nut, boss
plug, and the ballast air filter.
BALLAST AIR FILTER
CHECK AIRFLOW HERE
BY FEEL AND/OR NOISE
ADJUSTMENT SCREW
INSIDE STEM
LOCKING JAM NUT
BOSS PLUG
