What is the maximum hanger spacing for 3" steel except threaded light wall pipe?

The maximum hanger spacing for 3-inch steel pipe, excluding threaded light wall pipe, is specified as 15 feet according to industry standards and guidelines. This spacing is established to ensure that the piping system is adequately supported, minimizing sagging and movement that could potentially lead to leaks or structural failures over time. Proper support is critical in maintaining the integrity of the fire sprinkler system and ensuring optimal performance.

By ensuring the proper hanger spacing, the system can withstand vibrations and thermal expansions, which are common in piping systems. That said, the other options suggest distances that exceed the maximum recommended spacing. For example, 10 feet and 12 feet are within acceptable ranges, but they do not represent the maximum allowable distance. Distances of 20 feet exceed the standard, which could jeopardize the pipe's stability and overall function. Hence, the correct selection is 15 feet as it strikes the balance between adequate support and practical application for 3-inch steel pipe.