This cache is meant to be challenging and hints will be very limited. Please, do not provide additional information, photos of the cache or clues when you log this cache. Replace the cache as you found it please.
A fire riser is an exterior apparatus operated by a fire brigade to control a network of suppression sprinklers inside of a building. It is a series of pipes, valves, and pressure-regulators to direct the flow of water to the appropriate section of the structure. Using an open-ended wrench, the fire fighter division can manipulate the valves on a fire riser. These fire fighters often suffered injured-elbows due to how tight these valves were sealed to confine the high pressure of the water.
As a note: this building is abandoned and thus cachers should not attempt to enter the building or disobey the no trespassing signs on the fences. This cache is located on the street-side of the structure and is accessible to all with a pen included in the cache. I have adjusted the difficulty a half point on the easier side until I can make a few changes... Congrats to cachbefound on the FTF!