This video shows appropriate “drip rate” from a fire pump.
My Fire Pump is leaking! Is that OK?
In fire protection practice, the term “drip rate” almost always refers to the controlled leakage of water at the fire pump shaft packing, also known as the packing gland, on a packed centrifugal fire pump. This leakage is intentional, necessary, and required for proper pump operation.
NFPA 20, Standard for the Installation of Stationary Pumps for Fire Protection, requires that packed fire pump shafts operate with a slight, continuous leakage. While the standard does not prescribe a specific numeric value, industry practice has established a commonly accepted guideline:
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Approximately 2-4 drops per second is acceptable
This rate is widely used by pump manufacturers, inspectors, and service technicians as a practical interpretation of “slight leakage.”
Why Leakage Is Allowed—and Required
Controlled leakage at the packing gland serves several critical functions like lubricating the packing material, preventing overheating of the shaft sleeve, reduces friction and wear and extends the service life of the packing and shaft sleeve. Without this leakage, friction and heat buildup can rapidly damage pump components and compromise pump reliability during an emergency.
Certain leakage conditions indicate improper adjustment or maintenance and are not acceptable, like no leakage at all as this may mean that the packing is overtightened which can lead to overheating, accelerated wear and potential shaft damage. When there is excessive leakage or a steady stream of water coming from the fire pump this could indicate a worn packing, improper installation or insufficient gland adjustment. Both of these conditions should be corrected promptly to maintain compliance and pump reliability.
It is important to note that these drip rate considerations apply only to pumps equipped with packed glands. Mechanical seals are different and should exhibit no visible leakage during operation. A service technician can observe and verify the leakage during acceptance testing, during weekly or monthly inspections or after any packing adjustment or replacement.
NFPA 20 clearly establishes the principle behind packing leakage – the packed pump shafts shall have a slight leakage to provide lubrication and cooling.
While exact section numbers vary by edition, this requirement consistently appears in the chapters addressing pump components and shaft sealing arrangements.
A properly adjusted fire pump packing gland will always leak slightly—and that is by design. Understanding the purpose of the drip rate, recognizing unacceptable conditions, and applying NFPA 20’s intent ensures reliable pump operation, longer component life, and compliance with fire protection standards.