The net loss in flowing water pressure between any two points in a hydraulic system. It is the sum of friction loss, head loss, or other losses due to the insertion of an orifice plate, venturi, or other restriction into a section of pipe or hose
National Foam, A Firefighter's Guide to Foam (Foam Glossary), Kidde Fire Fighting, Exton, PA, USA 2008. http://www.zurichservices.com/zsc/pptlibrary.nsf/c e835d312fec922c862568010078a415/1808b7dc16b70efc06 25687f001364cf/$FILE/Firefighters%20Guide%20to%20F oam%20(National%20Foam).pdf, (Fom - Amer) {143}