So your new building will have a fire protection sprinkler system? And that means you’ll need a backflow preventer, right? In most cases, “yes.” But there are exceptions.
The International Building Code® (IBC®) and other similar documents define when a fire sprinkler system is required or when it’s advantageous to have one – since the code affords benefits for sprinkler-protected buildings. For non-residential buildings, the sprinkler system is typically designed to NFPA 13, Standard for the Installation of Sprinkler Systems. While the National Fire Protection Association (NFPA) 13 Standard for the Installation of Sprinkler Systems doesn’t require backflow preventers, the International Plumbing Code® (IPC®) usually does.
The Financial and Performance Cost of Backflow Preventers
Backflow preventers are designed to prevent the backflow of water from within a piping system, like a sprinkler system, back into the public water supply where it would contaminate drinking water and sicken the public. They work remarkably well, but they come at a financial and performance cost. Like everything else in life, backflow preventers are not free, and they’re not free of ancillary costs either. In addition to the initial cost of purchase and installation, there are added costs for annual testing as well as the costs of added complexity and pressure losses in the sprinkler system. For those working on Department of Defense projects, and applying Unified Facilities Criteria (UFC) 3-600-01, that pressure loss can be extraordinarily expensive.
Most backflow preventers impart a modest pressure loss (3 to 5 psi) on the water flowing through, but section 18.104.22.168 of UFC 3-600-01 -2016, states that the hydraulic calculation for a fire sprinkler system must include a 12 psi pressure drop across any backflow preventer, regardless of the actual pressure loss through the device. This may not sound substantial, but it could mean the addition of a $100,000 fire booster pump to overcome this non-existent pressure loss.
A Potential Substitute to Backflow Preventers
While we can’t ignore the pressure losses through a backflow preventer, there are circumstances in which we can eliminate the backflow preventer from the sprinkler system design. Section 608.16.4.1, exception 2, of the IPC® exempts dry-pipe, pre-action, and deluge sprinkler systems from the need for backflow prevention. This gives the engineer an opportunity to design a dry-pipe or pre-action sprinkler system for most buildings to eliminate the need for the backflow preventer. This will not be the perfect solution in every case because dry pipe and pre-action sprinkler systems are more complicated to install than wet-pipe systems, but if it provides an opportunity to eliminate a fire booster pump (and its direct and indirect costs), it may be the only difference between a project built to budget and one that’s not. Dry-pipe and pre-action sprinkler systems generally take a few seconds longer to deliver water to a fire, but they also offer advantages in cold conditions, and in areas like data centers, museums, and clean rooms where water-filled overhead pipes cause unwarranted anxiety to the occupants.
For more information on Fire Protection Systems Design contact Paul.Pinigis@MasonAndHanger.com.
Life Safety and Fire Protection Engineering & Consulting
Mason & Hanger offers fire protection engineering, code consulting, and life safety consulting as an integral component of our engineering services and as a stand-alone specialty service. The design of cost-effective and well-engineered fire protection systems requires a design professionals with best-in-class technical knowledge of fire protection systems and a thorough understanding of buildings and the construction process. Learn more here…