A packed gland seal, or the conventional shaft seal is not often used due to it's maintenance requirements. They require regular attention to adjust the amount of leakage, which is required to ensure proper lubrication of the gland packing. The life expectancy of a packed gland depends wholly on the liquid being pumped, with abrasive liquids reducing the life expectancy.

Packed glands are recommended for aggressive liquids. Also when a packed gland fails it simply begins to leak more and can be tightened to reduce the leak with the pump remaining in service, where as a mechanical seal leaks dramatically when it fails hence the pump will have to be taken out of service.

Mechanical Seals are more common. They are Maintenance free, and operate without any leakage. Again the life expectancy depends on temperature, duty cycle and product being pumped.

Both Packed glands and mechanical seals are parts which are subject to wear. Dry running will lead to the destruction of the seals.