Marina Dock Age, September/October 2003

Standpipe Systems: In Theory, Useful— In Practice, Unreliable?
by Gene Spinazola, P.E

Before investing in one of these systems, know what you are getting into,
and be prepared to pay a lot for a system you can count on

At a recent marina fire in South Carolina, the first responders on the scene hooked up a hose to the marina standpipe and charged (pressurized) the system. (A standpipe system consists of piping installed on the docks, designed to supply water to hose stations for the purpose of extinguishing a fire.) The system failed immediately, due in part to the sudden introduction of high-pressure water.

This happens time and again, even when the failed systems have been tested and accepted for service. One problem is that during testing the system is pressurized carefully and gradually—to 200 PSI—while at an actual fire scene the system will be charged rapidly, producing a momentary pressure spike that jars the piping and may cause it to burst or crack.

Beyond that, there are a number of potential complications with standpipe systems at marinas that can result in their failure. Accordingly, these systems are a subject worthy of some scrutiny. We can start with the National Fire Protection Association’s document, NFPA 303! section 4.4, which discusses fire standpipe systems for docks at marinas and boatyards.

(Most of the requirements for fire protection at marinas and boatyards are spelled out in NFPA 303: Fire Protection Standards for Marinas and Boatyards. The latest edition was issued in 2000. Occasionally, in sections of NFPA 303 there will be a reference to other NFPA standards. This may be just another means of getting you to buy more NFPA documents or an effort to refer you to a more detailed section already covered by another NFPA standard. Either way, the material is worth reading.)  

Section 4.4 spells out who needs to install a standpipe system along with some requirements that are specific to the marina industry. The actual design specifications for the system, however, are discussed in NFPA 14: Standard for the Installation of Standpipe and Hose Systems.

Who needs a fire standpipe system, and what does it require?

If the hose-lay distance from the closest possible location a fire truck can be positioned to the end of your dock exceeds 150 feet, technically, you need to install a Class-l standpipe system. The section goes on to say that piping for the system “shall be sized for the minimum flow rate for Class-II systems.”

The flow rate required for a Class-II system, at the most remote outlet, is 100 gallons per minute (GPM) at 100 Pounds per Square Inch (PSI). To meet this flow rate at the most remote outlet, the designer of the system will calculate the line losses due, in part, to the internal friction in the piping, number of bends in the pipe, and the number of fittings, such as elbows, tees, valves, etc.

Thus, to compensate for the friction losses and still meet the flow rate at the end of the dock, the supply pressure from the fire apparatus will need to be higher than 100 PSI. For example, if the friction loss is calculated to be 50 PSI, then the fire apparatus will need to pump 100 GPM at 150 PSI. Continue »