What is the pressure at the highest sprinkler head in a system?

The pressure at the highest sprinkler head in a system is determined by the hydraulic calculations used to design and assess fire sprinkler systems. In this context, the correct answer indicates that there is a pressure of 15 psi available at the highest sprinkler head, with a 7 psi residual pressure remaining during system operation.

This information is crucial because it provides insight into both the working or static pressure available at the sprinkler head when the system is operated and the residual pressure that ensures the system can still function effectively under various conditions. A 7 psi residual implies that even under flow conditions, the system maintains a minimum operating pressure, which is essential for effective sprinkler performance.

In fire sprinkler systems, it is vital to ensure enough pressure is available not just to activate the sprinkler but also to ensure that it can deliver the required flow rate necessary to extinguish or control a fire adequately. Therefore, understanding the pressure at the highest point helps in verifying that the system meets fire protection requirements and can perform as designed when needed.

By analyzing the choices given, it's clear that the pressures in the other options either do not provide enough context about residual values or suggest inadequate pressure levels for proper sprinkler function, marking them as less viable for a well-functioning fire protection system.