It should be noted that this memo is intended as a discussion draft and is not intended to address all of the issues involved. As such, the standard only requires a 10-minute water supply with a maximum design of two sprinklers flowing. SFM adopt a policy or interpretation not requiring either FDCs or the hydrostatic test for NFPA 13-D systems. It appears that there is a great deal of confusion concerning what type of water flow alarm is required on NFPA 13-D systems. Whereas the state fire and building codes require smoke detectors in both new and existing residences, the exception would prevail in most cases.
Most contractors install audible flow alarms as a normal part of installation.
An exterior flow alarm is, in my opinion, not necessary for most installations. The intent of exterior alarms is so that neighbors or passersby would hear the alarm and initiate rescue or call the fire department. Given climatic conditions in Minnesota and the frequency of windows being kept closed for great portions of the year, this is probably an unreasonable expectation. We have even discussed relaxing the requirements for exterior flow alarms under certain conditions during our code development deliberations. Even more distressing is having local municipalities impose requirements for central station monitoring.