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Experts in the design, supply, installation and commissioning of Dry and Wet Risers

Wet Riser

Wet Risers are installed in buildings for fire fighting reasons. Wet Risers are left charged with pressurised water from an in-house pump and storage tank which in addition is capable of being charged with water by pumping from fire appliance. 

A Wet Riser is required under the building regulations when a building has a top storey height above 50m from firefighting access level. 

Wet rising mains consist of vertical pipes similar to the dry rising main system with landing valves at each floor except the ground. The pipe system is connected to a permanent water supply normally a tank fed from the town mains. Duplicate automatic pumps, one duty and one standby supply this water to the pipe system.

The capacity of the water tanks feeding the wet riser should be such as to ,maintain a flow of water capable of supplying two fire-fighting jets for 45 minutes when water is being used at a rate of 1500 L/min.  

Where both pumps are electrically powered, a secondary power supply independent of the primary supply to the building, eg an automatically started generator or a supply from another substation, should be provided which, independently of the primary supply, is of sufficient capacity to maintain the pumps for wet fire mains in operation for at least 3 hours. 


Building top storey height less than 50M above fire fighter access level? A Dry Fire Mains may be suitable find out more

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Protection of Buildings under construction

In order that a fire occurring during the construction of a building can be dealt with effectively, especially in high or extensive buildings where large quantities of combustible materials might be stored, mains should be in an operational condition as soon as any floor of the building reaches 11m above fire service access level. These mains should be extended and commissioned progressively as work on the building proceeds to provide fire-fighting facilities at all stages of construction. 

Where wet mains are provided, installation initially can be as a dry main. When construction reaches 50m, the system should be commissioned as a wet main in accordance with the relevant recommendations of BS9990:2015. 

Maintenance Requirements

Inlets, landing valves, drain valves, door hinges and locking arrangements to the inlet and landing valve boxes should be inspected every six months.

Additionally, on an annual basis, a Static Pressure Test, flow and pressure test plus pump test should be conducted in accordance with section, and of BS9990:2015. 

The services of a competent person should be obtained to carry out maintenance and repairs. 

Contact React 4 Group to discuss your project or maintenance requirements. 

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