There are several codes and standards that call for the use of Hydrostatic Relief Valves (HRV) and often times the implementing organization fails to meet these requirements fully. As for propane systems, both OSHA and NFPA, require the installation of HRVs EVERYWHERE there is a chance that liquid propane can be trapped, but as this Nevada LP Gas Board Inspector states, many find excuse after excuse not to install these HRVs. Here is his story and a VERY GOOD scenario that many never consider when justifying these valves are not needed. Although a particular valve has “never been closed” does not mean it can not be closed!