Viking VK-1230 and VK-200 Fire Extinguishing Systems utilize hoses (or pipe) and NPT connections to attach the system’s container assembly to the system’s downstream nozzle pipeline. The NPT connection is used as an adapter between the cylinder valve and the pipeline, or between the hose and pipeline. A flexible steel hose is available as an option: Hose with straight connection Hose with 90° bend The hose has steel connectors on both ends with two thread size options: 1-7/8" UN x 1-1/2" ISO (for use with the 140 lb. cylinder assembly) 2-1/2" UN x 2" ISO (for use with 280 lb. and 390 lb. cylinder assemblies) For Multi Container Systems, a check valve is required between the hose and the manifold for each cylinder. A check valve ISO-NPT adapter is required for connecting the check valve to NPT threaded pipe or hose. Multi Container Systems also utilize pilot line(s) to connect the master cylinder to an additional cylinder (and each consecutive cylinder). The last cylinder is required to have a pilot line safety valve (equipped with a vent hole) for dissipating a slow increase in pressure.