What is Hydrostatic Testing of Portable ABC Fire Extinguishers? Written by Metro Fire on March 31, 2018. Posted in News, Testing Have you been told, “Your fire extinguishers are due for hydro testing”? The following link explains what hydro testing is and how it is completed. Click Here to Read the Koorsen Fire and Security Blog Post Tags: Fire Extinguishers, NFPA Trackback from your site. Leave a comment You must be logged in to post a comment.