Fire and Emergency Services Training Institute (FESTI) Exam 4 Practice Test

Wet-barrel hydrants are kept full of water in the barrel and the supply lines at all times, so when you open the nozzle or outlets, water flows immediately. There’s no waiting for the line to fill or for pumping to happen—the system is already pressurized with water. This readiness is what makes a wet-barrel hydrant distinct. In contrast, dry-barrel hydrants keep the barrel and sometimes the supply line dry to resist freezing, and water must be introduced when the hydrant is used. A check valve might be present on some hydrants but doesn’t define a wet-barrel design, and pumping isn’t required for a wet-barrel hydrant to deliver water.