Perhaps you’re thinking of how the jockey pump and main pump work together in a sprinkler system. A jockey pump maintains pressure in the system and is sized a

Perhaps you’re thinking of how the jockey pump and main pump work together in a sprinkler system. A jockey pump maintains pressure in the system and is sized at less than the flow rate of one sprinkler head. The main fire pump is activated when a pressure transmitter detects a drop in pressure. The jockey pump can’t maintain pressure when a sprinkler head opens, and the drop in pressure starts the main fire pump.