What nominal size should the fittings of the pressure sensing lines be?

The correct answer is based on standard practice in the installation of pressure sensing lines for sprinkler systems. Typically, pressure sensing lines are designed to ensure accurate readings without causing unnecessary pressure drop or flow restriction.

Using a nominal size of 1/2" for the fittings allows for sufficient flow of the pressure sensing medium, which is usually water or a non-freezing liquid, while still being manageable in terms of installation and compatibility with various sensors and gauges. A smaller diameter, like 1/2", is generally adequate for the low flow conditions commonly encountered in these applications, ensuring that the pressure readings are both accurate and responsive.

Larger sizes, such as 3/4", 1", or 1 1/4", could lead to increased costs and more complex installation without providing any significant benefits in performance for pressure sensing lines. Thus, a nominal size of 1/2" strikes an ideal balance for functionality, efficiency, and compliance with industry standards for pressure sensing applications in sprinkler systems.