Boyertown Furnace RSM 500 Installation, Operation And Maintenance Manual page 23

REQUIRED TO MAKE IT. This problem becomes proportionately larger with underground tanks.
Connect vacuum gauge to oil pump. Suction vacuum must not exceed 10 inches of mercury for single
stage pumps and 15 inches for two stage pumps. It is preferable to stay below these limitations. When
the suction line is tight and properly installed the pump will hold its vacuum for a minimum of 60
minutes after shutdown.
Outside Buried Tank Lift System
Inside Tank Gravity Feed System
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