NFPA 13 (2022) Section 16.4.5 with ‘enhanced content’ and some new standard language, discourages this practice. How will the requirement of Section 16.14.5.1.1 be achieved without additional calculation?:
16.14.5.1* Backflow Prevention Valves. A test connection shall be provided downstream of all backflow prevention valves for the performance of forward flow tests required by this standard and NFPA 25 at a minimum flow rate of the system demand including hose allowance where applicable. ENHANCED CONTENT ASK THE SYSTEM DESIGNER Is a main drain connection sufficient means for conducting the flow test at system demand required by 16.14.5.1? This type of connection generally is not sufficient for conducting the flow test because main drains have not been sized to accommodate system flow. Backflow preventers have internally loaded springs that are constantly pushing the valves into the closed position. If the springs are not periodically exercised, they might not permit the valve to fully open when there is a fire, impairing the sprinkler system. To prevent that from happening, NFPA 25 requires periodic forward flow tests of the backflow devices at the system demand flow. To ensure that the tests can happen, NFPA 13 requires the installation of a mechanism downstream of the backflow device that will allow the system demand to flow through the mechanism when it is opened. Prior to the 2016 edition of NFPA 13, the largest main drain size was limited to 2 in. (50 mm), which allowed systems to be drained in a reasonable time period and conserved water during main drain tests. In the 2016 edition, the size of the main drain was permitted to be increased, but using large main drains to conduct forward flow tests of backflow preventers still might be a concern. To create a flow at least as large as the system demand, an opening needs to be created with roughly the same cross-sectional area as the system riser. Doing so ensures that the system demand has been created when the mechanism is fully open without having to take any pressure or flow readings. On systems with a 2 in. (50 mm) main drain, the cross-sectional area of the drain opening typically is insufficient to achieve the system demand flow. When a main drain larger than 2 in. (50 mm) is used, the size of the system riser creates two potential problems. The first is that main drains generally are on the inside of a building, and providing sufficient drainage to deal with the discharge from the fully opened drain is a challenge. With 2 in. (50 mm) drains, sprinkler contractors frequently do not deal with the drainage situation correctly, and the drain cannot be opened fully. Using a larger drain might only exacerbate the issue. The second problem is the main drain test itself, which requires the drain to be fully opened four times annually. With a large drain, water is wasted when the drain is fully opened. It might be tempting to not open the drain fully for the test, which makes comparison of the test results impossible to correlate. A better solution would be a means to test the full flow of the backflow device that is separate from the main drain that allows for proper drainage. Paragraphs 16.14.5.1.1 through 16.14.5.1.3 are new for the 2022 edition and provide installation options to facilitate forward flow testing for systems equipped with backflow preventers. 16.14.5.1.1 A 2 1⁄2 in. (65 mm) hose valve shall be provided downstream of the backflow prevention valve for every 250 gpm (950 L/min) of flow rate required by the system demand including hose allowance where applicable. 16.14.5.1.2* Existing hose connections downstream of the backflow prevention valve shall be allowed to be utilized. 16.14.5.1.3* Other means shall be permitted as long as the system doesn't require modification to perform the test and it is sized to meet the system demand. Hope this helps, Ryan L. Hinson, PE*, SET** \ Burns & McDonnell Associate Fire Protection Engineer O 612-900-3755 \ M 763-688-4045 \ F 952-229-2923 [email protected]<mailto:[email protected]> \ burnsmcd.com<http://www.burnsmcd.com/> 8201 Norman Center Drive, Suite 500 \ Minneapolis-St. Paul, MN 55437 *Registered in: AK, LA, MD, MN, PA, TX, & UT **NICET IV - Water-Based Systems Layout [cid:[email protected]] From: Dennis Wilson <[email protected]> Sent: Wednesday, December 14, 2022 11:01 AM To: Discussion list on issues relating to automatic fire sprinklers <[email protected]> Subject: [Sprinklerforum] Re: BFP on underground supply On backflow testing, NFPA 13 (2019) 16.14.5.1 states the backflow needs to be tested at system demand. I have a hard cover copy, and in it the question was asked, if a 2” main drain would be sufficient, to do the backflow test. After their explanation, they say it basically needs to be the same size as your system riser, and using a larger drain valve would be a waste since the drain test is to be done more often. So what we’ve been doing is running a pipe outside the same size as the backflow, using a normally closed butterfly valve. Sometime routing around the FDC if it’s a Storz. model. Our thought now is why not run several 2” drains out the wall. With 2½” & 3” backflows, we increase the main drain to 2” which is usually enough for system demand. Can always run a separate 1” insp. test also. With 4” backflows, you already need (1) 2” main drain, why not run a separate one for testing, that will give you (2) 2“ openings, and run a third if you have a 6” backflow. And with multiple systems, run the main drains out separately instead of combining them together before you go out. Does this sound feasible, since all we’re really trying to do is exercise the springs in the checks? From: Ed Kramer <[email protected]<mailto:[email protected]>> Sent: Friday, November 18, 2022 11:19 AM To: [email protected]<mailto:[email protected]> Subject: [Sprinklerforum] BFP on underground supply NFPA 13 is pretty clear that some method of forward flow testing a fire sprinkler system backflow preventer shall be provided. If the BFP is located at the system riser (very common in these parts), we provide the required means. So, who is responsible for providing the means if the BFP is located in a pit on the underground fire service, and the UG fire service (along with the pit/BFP) is “by others”? From a practical viewpoint, it’s easy enough for us to provide that at our system riser, but are we required to do so? Or does that responsibility fall on whomever installs the BFP? I’ve not seen this addressed anywhere in bid/contract documents. Ed Kramer Bamford Fire
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