What Is The Difference Between A Dry Riser And A Wet Riser?

Fire services use dry and wet risers to provide a readily available means of delivering sufficient water to fight fires on the upper floors of tall buildings. However, these two systems work differently. A dry riser is a system of pipes and valves that fire services charge with water from the base of the building, whereas a wet riser is permanently charged with water by pumps and tanks.

Dry And Wet Riser Differences

Dry and wet risers perform an identical function in buildings – to deliver large quantities of water to the upper floors capable of putting out fires. However, the way they work is slightly different.

Dry risers are not pressurised. Instead, they rely on an inlet breeching at ground level that fire crews use to feed water into pipework that runs up the building. During a fire situation, fire services connect the inlet to a pump and water supply, pushing it up to higher levels. Crews then climb the stairs with lightweight hoses, attach them to outlets on the appropriate floor, and begin fire-fighting.

By contrast, wet risers are constantly pressurised and charged with water, reducing the number of steps fire crews must perform when they arrive at the scene of a fire. Tanks and pre-installed pumps push water to the upper levels, making wet riser outlets ready to fight fires at any time to alleviate any hot spots.

That said, wet risers’ basic structure is almost the same as dry risers. Both utilise pipes running up the core of the building and outlets on each floor. The pipes are usually between 100 and 150 mm in diameter and run internally or externally. There are outlet valves at each landing and two or four-way inlet connections at street level in boxed steel cabinets with glazed doors.

The following table covers the differences between dry and wet risers in more detail:

The differences between dry and wet risers

Feature	Dry Riser	Wet Riser
Purpose	To provide fire crews with a means of pumping water to the upper levels of a building	To provide readily-available water to fire crews on upper levels without the need to install a pumping mechanism first
Installation	Typically installed in buildings with no pre-existing water supply	Typically installed in buildings with permanent water supply
Construction material	Steel	PVC or steel
Pressurisation	Requires air pressurisation before use	Comes pre-charged with water
Maintenance	Requires regular maintenance to ensure correct air pressure	Requires less maintenance due to being pre-filled with water
Cost	Generally more expensive than wet risers due to the need for an air pressure system	Generally more affordable because an air pressure system is not required
Water pressure	High water pressure due to the air pressure in the system	Lower water pressure because it relies on existing pumps