Frymaster BIH series - Manual (Page 19)

4-6
When the filter pan empties, bubbles will
form in the frypot. Allow bubbling to continue
15-20 seconds to ensure the oil return lines
are clear of residual oil.
Turn off filter pump.
Top up oil level. Some oil may be lost in
filtering process.
Fill to top mark (arrow) in frypot. Remember,
the oil is at operating temperature.