By Larry Davis
Published Monday, March 31, 2008
| From the April 2008 Issue of FireRescue
As I’ve mentioned in previous columns, although it’s been part of the fire service vocabulary for decades, the term “dry hydrant” is really a misnomer. A more correct term would be “fire department suction pipe,” because the pipe, along with the fittings, is really an extension of a pumper’s suction system.
The actual installation of a dry hydrant is really pretty simple. However, as society becomes more and more sensitive to altering waterways and endangering wildlife, installing a dry hydrant in a public waterway can require a great deal of work. You must get the necessary approvals from all the various local, state and federal agencies that may be involved, which requires time and navigation through a great deal of red tape.
Maryland Sets the Example
Maryland fire departments in Carroll, Montgomery and Frederick counties have long relied on dry hydrants for use in rural water supply operations. Recently, to get around the increased scrutiny and lengthy approval process of installing a dry hydrant, several fire departments in Maryland have switched to installing an articulated suction pipe that doesn’t require the pipeline to be permanently installed into a stream or other body of water.
(In the interest of full disclosure, I serve as vice president for GBW Associates, LLC, which designed the following suction pipes.)
The Urbana Installation
Figures 2–6 show an articulated suction pipe installed on a historic bridge over a stream in Urbana, Md., a city in Frederick County. The fire department wanted a suction pipe installed that would deliver at least 1,000 gpm without disturbing the historic bridge in order to minimize approvals for installing the piping.
The resulting design involved attaching a 6" PVC dry-hydrant swivel head and a 6" PVC piping section to the bridge without drilling any holes in it. High-strength marine-grade clamps were used to avoid altering the bridge, and an articulated PVC joint is located about 8 feet from the base of the piping riser. Attached to this articulated joint is a 16' length of 6" PVC pipe and a low-level dry-hydrant strainer.
A marine-grade hand-operated winch is attached to the bridge to allow for lowering and retrieving the actual suction pipe and strainer.
The Hyattstown Installation
The Hyattstown Fire Department (HFD) in Montgomery County had a perfect location for a suction pipe—along another historic bridge—but they too encountered the same issues of disturbing the concrete structure and needing approvals to dig a ditch into the waterway to permanently install the suction pipe. To avoid those problems, the HFD now uses the design shown in figures 7–9.
A parking area adjacent to the bridge provides a staging area off the road for pumpers connecting to the dry hydrant head. A standard 6" PVC 45-degree dry-hydrant head and piping were permanently installed (buried) in an area close to the stream. A 90-degree swivel is connected to the actual 6" PVC suction pipe and strainer. A cable is connected to both the strainer and a hand-operated marine winch, which raises and lowers the strainer.
As you can see from these photos, obtaining approvals for the installation of dry hydrants can be simplified when nonpermanent piping is attached to bridge structures. In these cases, the articulated suction pipes also simplify inspection and testing.
Although these are just a few examples of what some departments are doing to overcome the restraints associated with dry hydrant installations, hopefully they will assist you in developing a suitable solution for your response area. ’Til next time, stay safe.
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