What is a Backflow?
A backflow is when the water flows in the opposite direction in the sprinkler system piping. To put it simply, instead of the water flowing towards the sprinkler head, the water goes back towards the water source. This is not a good idea as stagnant water in the sprinkler lines can contaminate the water source if it streams backward. That's why it's vital to have backflow preventers in place.
What Are Backflow Preventers?
Fire sprinkler backflow preventers are devices in the sprinkler line that avoid the water from flowing towards the main water source. This will avoid contamination of the water. You can select from two types of preventers including:
RPZ Valve Assembly: The RPZ preventer is used when there are dangerous applications included, such as chemicals. They are more complex, however, just as reliable than DCVs. Generally needed for high-hazard settings, defined by the AWWA as those in which an unguarded cross-connection could introduce substances that trigger disease, death, or disease spread when presented into the public supply of water. Geared up with a hydraulically run relief valve in addition to 2 spring-loaded check valves.
Check Valve Assembly: Check valve assembly preventers are put in place when you have a conventional fire protection system. It is the most typical kind of backflow avoidance device. Ideal for low-hazard settings, specified by the American Water Functions Association (AWWA) as a scenario in which a cross-connection may create an annoyance or be visually undesirable. However, it would not develop a health risk. DCVs include an inlet shutoff valve, 2 separately operating spring-loaded check valves (generally inside a single valve body), four test ports, and an outlet shutoff valve.
Why Are Backflow Preventer Inspections Required?
When you have backflow preventers in location, you need to evaluate them frequently in accordance with regional guidelines in your area and National Fire Security Association (NFPA) standards. This assessment and testing must be done by a professional backflow tester.
The accredited professional will carry out a forward flow test and backflow efficiency test.
Forward Circulation Test-- Forward flow tests are performed annually in accordance with NFPA 25 at the designated system circulation rate. This test checks whether the system can get sufficient water supply in a fire condition.
Backflow Performance Test-- This test monitors the efficiency of your backflow prevention device to check that the water supply is safeguarded from cross contamination. This test is carried out after the forward flow test in accordance with the requirements of the authority having jurisdiction.
Risk of Not Having This Work Done
Without regular maintenance, a backflow prevention assembly can become jeopardized and begin to leak water back into the city's supply of water. This can take place for a variety of reasons. However, the most typical is from particles or sediment (that is naturally in water) entering of the backflow preventer. A dripping backflow preventer not just threatens the security of water but can likewise cause the fire sprinkler not to have enough water to work correctly when required.
A backflow inspection is needed yearly as established by the NFPA 25 Requirement for the Inspection, Screening and Maintenance of Water-Based Fire Defense Systems.
Backflow Preventers Are a Crucial Part of a Fire Sprinkler System
Backflow preventers offer an important interface between a building's fire protection system and the supply of water that feeds it. This is essential to prevent any prospective cross-contamination that can happen when water from the fire sprinkler streams backward into the water pipe, carrying with it potentially hazardous contamination into the general public's drinking water supply.
For example, the U.S. EPA reported a 1997 incident in which an approximated 40,000 neighborhood taps in Charlotte-Mecklenburg, North Carolina, were infected when a fire truck pump developed backpressure on a fire hydrant before the valve was closed. This triggered a pressurized backflow into the public water system of more than 60 gallons of liquid fire-fighting foam.
In Pittsburgh, Pennsylvania, in 2008, a comparable situation happened when water pressure from the city's fire engine linked to 2 fire hydrants and overwhelmed the city's drinking water supply lines. As in the 1997 event, this created a backflow that presented fire suppression foam into the water supply. While the foam did not position a considerable health threat, water users in the downtown area were informed not to use the water until the foam might be flushed from the system because it could irritate the skin and eyes.
According to the American Backflow Prevention Association, 6.2% of the pressure losses reported are due to fire-fighting activities. It is hard to say how often incidents like these now happen since the data is not available. But, the actual number is likely greater since lots of backflow events go unreported.
How Do They Work?
Backflow preventers are equipped with two one-way valves, called check valves, which enable the water to flow only in one direction. This redundancy ensures that if one check valve fails, the other will continue to protect the water supply and create a more trusted seal, which guards against small backflow leaks. The check valves in a backflow preventer operate individually with a differential pressure-relief valve in between them, enabling the closure of one valve to lower the pressure differential throughout the other.
If you wish to discover more about how a backflow preventer works, the American Water College supplies an excellent illustration in this video entitled “Backflow Prevention: Fire Hydrants and Valves”.
What are the Requirements for Backflow Preventers?
While the requirement to have backflow preventers in a fire sprinkler system is normally discovered in local pipe codes, their installation, evaluation, screening, and upkeep generally follow the National Fire Defense Association (NFPA) standards:
NFPA 13: Standard for the Installation of Sprinkler Systems
NFPA 25: Standard for the Assessment, Screening, and Upkeep of Water-Based Fire Defense Systems
Considering that local plumbing codes likewise govern backflow preventers, it is essential to contact your local water authority to figure out if there are any extra requirements for backflow preventers.
Some jurisdictions might allow alternatives to backflow preventers depending upon the particular circumstance. However, many water providers require backflow preventers on all fire department connections (FDCs) to guard against potential contamination from the non-potable water that firemen might generate from their automobiles to help fight a fire. This water is frequently treated with antifreeze, corrosion inhibitors, or extinguishing representatives, all of which could pose public health issues if they were to backflow into the water system. Therefore fire defense systems with FDCs are high-hazard scenarios with regard to backflow.
Checking and Maintenance Requirements
One may reasonably presume that NFPA 25 requires screening of any backflow preventers set up on fire sprinkler systems. This used to be the case. Nevertheless, the 2011 edition of the code removed this requirement-- that and all the editions published given that contain requirements for forward flow. The NFPA explained its decision to eliminate testing requirements for backflow preventers in the following way:
"While backflow remains a genuine health concern, avoiding it is now thought about outside the scope of NFPA 25. The basic presumes that regional or state requirements will continue to make sure that the devices are effectively tested by certified personnel."
This makes sense when one considers that the NFPA's primary focus is on fire security, not the defense of public water materials. Firefighters (and the NFPA) have an interest in making certain water will stream when needed, which is why forward circulation screening is still required.
Backflow testing is now regulated by local pipes code and generally required yearly, although it may be needed more regularly in some jurisdictions. Backflow tests generally take about 15 minutes to perform and involve trying to instigate a backflow under protected conditions to see if the assembly works effectively. If any water gets past the check valve, that device should be immediately repaired or replaced. Repairs can vary from easy things like replacing o-rings and rubber gaskets to changing one or both check valves or replacing the entire assembly.
It is important to always work with certified fire security experts when installing and checking backflow preventers in your fire defense system. Inappropriate setup of backflow preventers can cause premature failure, and inappropriate testing can damage the assemblies.