Fire Hydrants Overview
Dry Riser
This is normally dry but is capable of being charged with water by pumping from a fire service appliance via an inlet breeching fitted on the outside of the building at ground level. An air release valve is fitted at the highest point to enable the riser to be fully charged. There are fire hydrant gate valves on each floor so that the brigade can connect into the water supply at any level of the building.
Wet Riser
A wet riser is a pipe kept permanently charged with water which is then immediately available for use on any floor at which a fire hydrant globe valve (also known as a landing valve) is provided. Wet risers are necessary for buildings which are too high for brigade pumps to supply the necessary water pressure via a dry riser. If the mains pressure is higher than maximum brigade operating pressure it is necessary to use pressure regulating landing valves.