Relay Relief Valve : A pressure relief device on the supply side of a pumper intended to protect hose against the damaging pressure surges common in relay operations
Ralph W. Burklin & Robert G. Purington, Fire Terms: A Guide to Their Meaning and Use, National Protection Association, Boston, MA 1980 USA. (Guide: Meaning and Use, Nat Prot Association Fr Srvc - Amer) {457}