What is a Dry Riser?
A dry riser is an empty vertical pipe installed in a high building of over 18m but less than 60m tall. It allows firefighters to gain access to higher floors.
Usually, the ground floor has a dry riser inlet which can be connected to pump outlets of fire engines. The fire engines pump up water through the building, and pressurized water is distributed to various positions of the building.
What Does a Dry Riser Do?
In the event of a fire outbreak, firefighters use various techniques, tools, or machines to tackle a blaze in a building. However, things may be a lot difficult when firefighters need to carry heavy fire hoses through tall buildings. A dry riser, when installed, saves firefighters such stress and makes firefighting effortless.
Components of Dry Risers
Generally, dry risers contain three components. The components are the external inlets, pipework and outlet points.
External inlets must be easily accessible to fire service in case of emergency. The pipes contain the compressed air and must be fire-resistant. Pressured water passes through the pipework which is released in the outlet points.
The inlet is usually located at the ground level exterior of the building and must be at an 18m range of fire service access. The inlet is usually enclosed and is identified as ‘dry riser inlet’. There is usually a draining valve present on the inlet that drains water from the pipes after testing or fire services.
On most dry riser pipework is a valve that allows compressed air to escape when the pipework is charged with water. Layout, construction and designs of pipework can strongly determine the efficiency of a fire system when the need arrives.
Dry riser’s outlets are usually situated along stairways, cabinets, lobbies or enclosures. When installing, priorities are generally placed on escape routes.
Outlets also may be protected by breakable enclosures. Dry riser’s outlets are locally known as standpipes, landing valves or landing outlets.
Differences between Wet riser and Dry riser
For wet risers, water is kept permanently in pipes or rooftop tanks for manual or automatic fire fighting. Dry risers often come in handy when water pressure available in a building is insufficient to curb the fire, especially in cases where the pipes are blocked or frozen.
Wet risers can be used for buildings of any height. They are commonly installed for buildings that are taller than 60m. Dry risers, on the other hand, are restricted and are useful only in buildings that range between 18m and 60m in heights.
Wet risers are always pressurized because of the water is consistently in the pipes. Being regularly empty, you can identify a dry riser by their dependence on external pressure provided by the water moving in through the external inlet.
Installation and Recommendations
According to building regulations and British standards, there must be a fire appliance access within an 18m range of the dry riser inlet box. For outlets, they must not be more than 60m apart horizontally. Also, layouts, designs, landing valves, or outlets can affect the performance of dry risers, and consequently, the firefighting process.
Dry risers can be vertically installed in strategic and calculated positions in a building. The staircase, lift enclosures, cabinets, and other parts that would have little or no effect on water pressure when suppressing fire should also be considered when installing dry risers.
Therefore, if you need to install any riser, it is recommended that you employ IPAF or PASMA licensed engineers in the installation process.
How Often Should Dry Risers Be Serviced?
It is recommended that a dry riser system is visually inspected every six months. An annual service visit and ‘full wet’ testing are also recommended by British law to ensure the readiness of every equipment for immediate use in case of emergencies.
The inspection and tests are recommended because of possible cases of vandalism, leaks or malfunctioning valves or parts. It is the responsibility of building owners and managers to ensure that inspections of risers are done.
If a business building experiences a fire outbreak without a record of the previous inspection, the prosecution may be made.
What Buildings Have Dry Risers?
A dry riser is usually installed in buildings between 18m to 60m in heights. It is an equivalent of more than six-storey buildings and less than 17 storey buildings. If a building is taller than 60m, a wet riser must be used.
Finally, it should be noted that dry risers are not limited to high rise buildings. It is generally installed in any structure that may limit or restrict free access to firefighters. These buildings may include but not exclusive to car parks, hospitals, or multi-basements.