For water pumps gland packing is used to prevent any leakage from the shaft of the pump.
It is specifically designed to withstand extreme conditions.
Packing in a pump is intended primarily to restrict leakage around the shaft. It is intended to fill the annular space between the box and shaft so the packing may come as close as practical to the shaft or shaft sleeve without actually contacting it, and thus restrict the leakage. All packing manufacturers recommend a slight leakage through the packing for accomplishing water lubrication.