Drafting most always involves the use of water that has some type of debris or contaminant in it: pebbles, leaves, aquatic vegetation, silt, etc. It is very important to always take the time to back flush a fire pump after that pump has been used in a drafting operation. Because even though we use strainers and intake screens, foreign objects and debris can still make their way inside the pump and cause damage to various pump components and accessories.
The easiest (and probably best) way to backflush a fire pump is to use clean hydrant water from a municipal water system. However, in a rural area, such water may not be readily available. In that case, one may have to resort to using water "back at the fire house" to conduct the back flushing operation. Be sure to check all intake screens for blockage and contamination.
This hydrilla was caked against the intake screen of a fire pump and severely restricted the water flow.
Rocks and pebbles can also be very problematic. The screen may have to be removed in order to clean out the rocks.
Even dry fire hydrants can prove problematic. These pebbles were found after drafting operations were shut down.
The intake screen kept these pebbles from passing into the pump - however, much smaller ones probably made it through.
A fire pump's intake screen is designed to catch the "big stuff" - which this one did. However, a thorough back-flushing is still needed.