NFPA defines a standpipe as an arrangement of piping, valves, hose connections, and associated equipment installed in a building or structure, with the hose connections located in such a manner that water can be discharged in streams or spray patterns through attached hose and nozzles, for the purpose of extinguishing a fire, thereby protecting a building or structure and its contents in addition to protecting the occupants.
Standpipe systems are a network of piping in a building fed by a water supply and featuring numerous outlets for the water. They are essentially indoor fire hydrants that allow occupants, firefighters, or both to access water to fight fires. And just like the elevator brake, they have made the construction and safe use of tall buildings possible.
Types of standpipe systems
There are three classes of standpipe systems:
Class I: A Class I standpipe system shall provide a 2 1/2 inch hose connection for use primarily by trained personnel or by the fire department during initial response. This class has no hose attached. The fire department will usually carry hose packs to the floor level, typically a stairwell, where they will start their operations and connect to the standpipe system. These connections must match the hose thread utilized by the fire department.
Class II: A Class II standpipe system shall provide 1 1/2 inch hose stations to supply water for use primarily by trained personnel or by the fire department during initial response. These are typically found in cabinets with 100’ of hose.
Class III: A Class III standpipe system shall provide 1 1/2 inch hose stations to supply water for use by trained personnel and a 2 1/2 inch hose connection to supply a larger volume of water for use by fire departments and those trained in heavy fire streams. Many times these connections will provide a 2-1/2 inch reducer to a 1-1/2 hose connection.
Basic components of standpipe systems
While each system can vary, a standpipe generally consists of an interconnected series of pipe, pumps, valves, alarms, drains, and fire department connections. Over the course of this article and the next, we’ll discuss each of these components in detail including maintenance and regulatory requirements. So, without further ado …
The most extensive component of a standpipe system is the network of pipes which carries water throughout the building. The National Fire Protection Association (NFPA) specifies different requirements for the material used in underground pipes and above-ground pipes.
Underground pipes are defined as those “buried in soil” and they must be made of lined ductile iron, cement, copper, brass, or plastic. Steel pipes are not permitted underground, as they tend to corrode quickly in the soil.
Above-ground pipes include those found in underground basements and garages, as well as the pipes that travel throughout the rest of the building. They can be composed of steel, ductile iron, or copper, with steel being the most popular choice. This metal is often chosen because it is sturdier than ductile iron and less expensive (and less subject to theft) than copper.
The diameter and thickness of the pipe used in standpipe systems are determined by specific hydraulic calculations about required system pressure and demand based on the size and height of the building. That said, NFPA 14 requires that standpipes be at least 4” (100 mm) in size, whereas pipes that are part of a combined standpipe/sprinkler system need to be at least 6” (150 mm).
Fire pumps are the on-site mechanism that supplies pressurized water for automatic and semiautomatic standpipe systems. Manual standpipe systems do not need them since the fire department supplies the water and pressure from trucks when firefighters arrive on the scene. The right fire pump for a standpipe system depends on the pump’s size and flow capacity relative to the system demand of the standpipe it will serve. Most standpipes have a system demand of 750, 1,000, or 1,250 gallons per minute (GPM), and a pump can be used to supply a system that has a demand of 100% to 150% of the pump’s flow capacity.
For example, a fire pump that is rated at 500 GPM can be used for a standpipe with a system demand of 750 GPM, though a pump with an exact rating of 750 GPM is also commonly used. Using pumps with a greater flow rate than the system demand isn’t advisable for two reasons: It has the potential to apply too much pressure to the system, and larger pumps are more expensive.
The requirements for regular inspection and maintenance of fire pumps are extensive and exhaustively detailed in Chapter 8 of NFPA 25. Table 188.8.131.52 below lists all of the necessary actions:
Every standpipe system (with the exception of the manual dry variety) requires that a water flow alarm device is installed in a portion of the piping between the water supply and the initial hose connection.
This alarm sounds to provide notice that the system is engaged during a fire. It also gets the attention of personnel who can assess whether there is indeed an emergency; if not, these alarms could prevent water damage in a compromised system.
Gauges are required in numerous portions of standpipe systems. They provide a pressure reading during testing conditions and assess the normal operating pressure of the system. Gauge locations include:
- At the top of each standpipe (required)
- At every water supply connection (required)
- Upstream or downstream of any master pressure regulating assembly (required)
- Above and below each alarm check valve, dry pipe valve, deluge valve, backflow preventer, or system riser check valve (required)
- At hose stations which have a pressure-reducing valve (optional)
Due to the importance of monitoring your standpipe system, maintaining the gauges is especially critical.
Fire department connection
The fire department connection (FDC) is an essential component of manual wet and manual dry systems, which will not work without firefighters supplying water and pressure to the system.
That said, FDCs are still required in all Class I and Class III systems, even those with onsite fire pumps that serve the express purpose of supplying pressurized water. The rationale for requiring FDCs in these systems is simple: If a fire pump malfunctions during an emergency, the FDC provides a backup.