In establishing a constant pressure relay, what do pumpers need to do after hooking up their apparatus?

• A. All pumpers, except the source pumper, open their discharge valves on dump line
• B. Only the attack pumper opens its discharge valve
• C. All pumpers disconnect their hoses
• D. Source pumper supplies water without any other pumpers connecting

Answer: (A)

In establishing a constant pressure relay, it is necessary for all pumpers, except the source pumper, to open their discharge valves on the dump line. This step is crucial because it allows the system to balance the water flow and ensures that pressure remains constant throughout the operation. The source pumper, which is responsible for supplying water, does not open its discharge valves in this case; instead, it maintains a steady flow to support the other pumpers.

When each of the other pumpers opens their discharge valves, it facilitates the transfer of water from the source pumper through the relay to the attack line, aiding in maintaining consistent pressure. This simultaneous opening of discharge valves allows for a coordinated effort among the pumpers to optimize the water supply to the attack pumper, which is essential during fire suppression.

Other choices do not correctly reflect the operational procedure required for maintaining a constant pressure relay. Disconnection of hoses or limiting the actions to a single pumper would disrupt the pressure consistency essential for effective firefighting efforts.