Piezometer Ring : A fitting inserted in a water line to measure precise water pressure; it has a pressure gage and a series of holes around the interior that connect to a chamber
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}