Benefits and Drawbacks of Flexible Sprinkler Drops

While not a code requirement, flexible sprinkler drops have quickly become a major innovation for the fire sprinkler industry. This week's post explores logistical advantages and drawbacks of the technology.

​Components

Components of a Flexible Sprinkler Drop Assembly

Advantages
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Reduced labor cost

• Flexible sprinkler drops can significantly reduce the time to installation. A single return bend on branch piping can be composed of at least seven distinct pieces which include some that must be cut and joined. A flexible sprinkler drop does not require the assembly nor coordination required to locate in specific positions within a ceiling.

Faster project completion

• Time savings can lead to an overall faster-completed project.

Allows for ceiling/lid movement over time 

• Lowering of a ceiling or hard lid can occur over time due to settling, loads placed on the ceiling, or even activity above the ceiling (such as workers above a cooler/freezer). This difference in ceiling position for hard piped sprinklers can cause unwanted obstructions between the new ceiling position and the fixed-in-place sprinkler. Flexible drops allow the sprinkler to move with the ceiling.

Flexible sprinkler drops allow the sprinkler to stay in the appropriate position with ceiling movement or following seismic events

Seismic performance

• In a seismic event, sprinklers on flexible drops can continue to provide protection below a ceiling

Does not require oversized escutcheon 

• Unless a ceiling is rigidly braced, sprinklers must be allowed 1/4 inch clearance on all sides in buildings with Seismic Category C (ASCE 7 Section 9.6.2.6.2.1) or 1 inch of free movement in all horizontal directions in buildings with Seismic Design Category D, E, and F (ASCE 7 Section 9.6.2.6.2.2(e)).
• This requirement necessitates either (1) an oversized escutcheon to cover the required clearance (which may not exactly enamor your architect), (2) a swing joint above the sprinkler, or (3) a flexible drop. While each solution meets code, flexible drops can accommodate the required movement without oversized escutcheons (NFPA 13 2016 9.3.4.11.1).

For facilities with Seismic Design Category D, E, or F, movement must be allowed between a sprinkler and its surroundings. Oversized escutcheons are one method to allow the movement but conceal the surrounding gap.

Remodel friendly

• Use of flexible sprinkler assemblies allow easy relocation of sprinklers within a short distance with ceiling modifications without re-cutting, attachment or demolition of existing pipe and fittings.

​Disadvantages

Material Cost

• A flexible armover assembly can run $160-$400 per assembly, while traditional pipe and fittings can run half that cost or less on materials.

Hydraulic Demand

• As we'll explore in next week's post, the hydraulic demand can be dramatically more significant than a return bend, adding the equivalent of up to 100 feet of 1-inch schedule 40 piping in friction loss.

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​What is your experience?
Join the conversation and discuss what you see as advantages or disadvantages of flexible sprinkler assemblies for this post at www.meyerfire.com.

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Next week I'll explore points to consider with flexible sprinkler drops in design and inspection that I've come across in my research.

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