Water leaking from a valve stem or gland is usually caused by ___

• A. Worn packing
• B. Excess packing
• C. Damaged stem
• D. Dried out packing

Answer: (D)

Valve stem packing forms a seal around the moving stem, and its effectiveness depends on its ability to stay pliable and properly compressed by the gland. When packing dries out, it loses elasticity and shrinks, creating small gaps that allow water to seep along the stem and out of the gland area. This is why dried out packing is the usual cause of leakage at a valve stem. While worn packing can also leak, aging packing is more likely to dry and lose its sealing capability; excess packing tends to cause binding rather than a direct stem leak; a damaged stem would allow leakage through the stem material itself rather than around the packing. Replacing the packing and properly adjusting the gland restores the seal.