Proper dry riser installation is important for high-rises. In tall buildings, there is a need for an effective firefighting system that can cover all the floors. A rising main is a vertical pipe with an inlet on the outside of the building and outlets on every floor. The outlets are inside cabinets, which allow firefighters easy access. In case of a fire, firefighters pressurise the main so that there is a free flow of water. For safety purposes, dry riser installation needs to follow specific regulations which we will discuss below.
What Is a Dry Riser? (UK Fire Safety Standards)
Rising mains can be either wet or dry, depending on whether or not they have water in them. A dry riser has no water in it, so a fire truck must be connected to the inlet at ground level. This then provides a steady stream of water that comes out of an outlet on the desired floor. There should be a dry riser outlet on each floor of a high-rise building. This enables firefighters to get to a specific floor without having to drag a hose from the fire truck up the stairs. In residential buildings, dry risers need to be within a fire resistant shaft.
Under UK regulations, dry risers are a requirement for buildings over 18m tall, but less than 60m. This translates to about 6 stories and above, but less than 17.
Key Components of Dry Riser Installation
Dry riser installations consist of three main components which follow specific regulations:
External Inlet
An external inlet needs to be located on the exterior wall on the ground floor. It should sit within an enclosure with a sign indicating that it is a dry riser inlet. The enclosure should hold a collecting head with no less than two instantaneous male hose connections and a drain down valve. This allows the fire and rescue service to access the inlet quickly and for the inlet to be effectively drained after use. The enclosure requires a key to open, but also has a small glass window that can be broken for fast access. You have to position an external inlet close to the street, since a fire truck has to park within 18m of the inlet. The inlets and their housing should comply with the BS5041 standard and the BS 336 standard regarding fire hose couplings and ancillary equipment.
The Piping
The pipes should have an internal diameter of 100mm for buildings with a single outlet on each floor. Taller buildings and buildings with more than one outlet per floor, the pipes should have an internal diameter of 150mm. The top of the piping needs to have an air valve for evacuating the air inside the pipes once water starts running through them. The piping must be made of materials specified in the regulations. They should also have fire resistant shafts around them.
Outlets
Outlets on each floor allow firefighters to attach their hose to the dry riser and pump the water from the fire truck. They need to have one or two instantaneous female hose connections and a large gate valve. The connections should follow BS 336 specifications.
You may fit the outlets within an enclosure with a glass window for fast access. The outlets should be located in a fire escape staircase or similar protected location. Adding an outlet on the roof level allows easy testing without making a mess on one of the floors. You need to have one outlet for every 900m2 of floor. If there are multiple outlets on a floor, they should be within 60m of each other, so that no part of the floor area is more than 60m away from an outlet. You need to place the outlets 750 mm off the floor, according to BS 9990.
UK Regulations for Dry Riser Systems (BS 9990 Compliance)
There are several things you have to take into account when installing dry risers:
- You should use galvanized wrought steel pipes and fittings;
- You must secure a planning permission and follow specific building regulations during installation;
- You should consult your local fire station regarding the proper placement of all the dry riser components. It is important that all the elements fit the equipment a fire station uses;
- The dry riser installation needs a water supply nearby to ensure that the firefighters have enough water to work with;
- A competent person needs to perform an inspection of the dry riser every six months, with the annual inspections being more thorough.
You need to comply with all of the above regulations if your building is required to have a dry riser for fire safety.
How to Test and Maintain a Dry Riser System
Since a fire and rescue service needs to be able to act quickly in an emergency, you need to make sure that the dry riser is in good working condition. If your building is at special risk, you should provide detailed information on your dry riser in your risk assessment data.
You should visually inspect all the elements of the dry riser every six months and have a detailed inspection and servicing done by a professional every year. This is according to BS 5306: Part 1 and BS 9990. Each year, a full wet test should also be carried out. For the purposes of the test, you’ll need to pressurise the mains to 150 PSI or 10 Bar and run water through the pipes. This is why the roof level outlet is recommended.
Your local fire and rescue service may be able to assist you during an annual test. Some British fire and rescue services will charge you a fee for this service, so check with them to find out more about dry riser installation and maintenance.
