This paper discussed about the challenge in operating light naphtha pumps with small vapor pressure to seal chamber pressure margin which had resulted to multiple mechanical seal failures. After thorough investigation, manipulating the pumps? seal flushing plan and reinstating the pumps? throat bush were the key success factors which successfully improved the mechanical seals? reliability. Lesson learnt from this incident is valuable to prevent similar failures to take place, especially to pumps with small vapor pressure margin.