The barrel strainer must be submerged at least __________ below the surface of the water for a pumper service test.

The correct answer indicates that the barrel strainer must be submerged at least 2 feet below the surface of the water for a pumper service test. This requirement ensures that the strainer can effectively draw water without pulling in air or contaminants. Submerging the strainer a sufficient distance below the water surface allows for an uninterrupted flow, reducing the risk of cavitation and ensuring that the pump operates efficiently during the test. It also helps to mitigate the chances of drawing in debris or floating material, which could impair pump performance or damage the apparatus.

For optimal operation and testing, adherence to manufacturer guidelines and industry standards regarding the depth of the strainer is critical. This depth is often specified to ensure testing conditions closely mimic real-world scenarios where the water source may not always be perfectly clear or deep. Therefore, the 2-foot requirement is a balanced approach to ensuring system reliability while preventing operational issues during the pumper service test.