Mar 7, 2022
On the 30th solocast episode of Fire Code Tech we are talking about flow tests. We get into codes and standards key definitions, and tips/tricks for professionals around flow tests. Tune in to find out when you need to perform hydrant
Transcription
Hello. Welcome to the solo cast of fire code tech in these episodes. It's just gonna be me, your host, Gus Gagliardi. There's gonna be a range of topics, but I'm gonna talk about specific technologies, installation, standards, codes, and how they work as well as some other interesting topics that don't neatly fit inside of the context of a normal I.
Hello. All welcome to the 30th episode of the fire code tech solo cast. On this episode, we're talking about flow tests. Yes. I went to a conference recently and was asking, um, some design and plan review professionals, what they found to be the most commonly missed piece of design documents. And the consensus in the room was that water supply information was a big piece that was commonly left out of the puzzle.
So I wanted to talk about what a flow test is. How do you perform a flow test and some key terms and definitions, and talk about N FPA 2 91. Don't forget to subscribe. So you never miss an episode and follow us on social media oppose most frequently on linked. Also, if you wanna do me a huge favor, go ahead and give us a five star review wherever you listen to your podcasts.
So what is a flow test? Let's talk about the, I always like to start with, you know, really just define what we're talking about. What is this subject in fire and life safety? So NFPA 2 91 is titled as the recommended practice for water flow testing and marking of hydrants. There's an important distinction between a code, a standard and a recommended practice.
NFPA 2 91 is not referenced by the international building. Which means that it does not have the enforcement of law. Now, there might be an FPA documents, like an FPA 13 or an FPA 24 that have. Requirements in them to use N FPA 2 91, but in specific it is not referenced in chapter 35 of the international building code.
So is looking for the definition of a flow test. And I was assuming it would be in, in FPA 2 91, but that's not the case. I did. However, find a definition of a Flo test in NFPA 13, that was referenced from NFPA 20. N F P 13 is the standard for installation of sprinkler systems in NFPA 24 is the standard for the installation of private fire service mains and their Pences the definition in the 2019 edition of NFPA 13 for flow test under section 3.3 0.8.
Zero is a test performed by the flow and measurement of water from one hyd. And the static and residual pressures from the adjacent hydrant for the purposes of determining the available water supply at that location. So in broad terms, we use flow tests to establish water supply criteria. Why is this important?
You might ask, well, flow tests are the basis for all hydraulic calculations. So in order to perform valid hydraulic calculations for sprinkler systems, You need some water supply data in order to determine if you need a fire pump or a fire protection water storage tank, it's an oversimplification of the process, but fire pumps are generally required when there is a deficient pressure in your municipal or private water supply and fire protection, water storage tanks are required when there is inadequate.
So as a quick recap, a flow test is used to determine water supply, and there are several standards and recommended practices around the subject that are very useful. NFPA 13, NFPA 24 and NFPA 2 91 all have information about flow tests. So you should investigate all of these standards and recommended practices.
When you are doing research on flow tests. as additional framing for the conversation. There are a couple key terms that are very important when discussing flow tests in its most elemental pieces, static pressure, residual pressure and flow are the data points that are being interpreted for the water supply.
The more accurate data as close as possible to your facility that you can. the easier it's going to be to perform your hydraulic calculations. Static pressure is defined in NFPA 2 91 as the pressure that exists at a given point under normal distribution system conditions measured at the residual hydrant with no hydrants flowing.
so that's a long drawn out way to say a pressure reading wall. Water's not flowing. So static refers to, uh, pressure measurements while the hydrants are not open and not flowing water. So I guess you can imagine what residual pressure. residual pressure is defined. Just one section above in 3.3 0.3 and N FPA 2 91 has the pressure that exists in the distribution system.
Measured at the residual hydrant. At the time the flowing readings are taking at the flow hydrants. So residual pressure is a measure of pressure while the system is flowing water. So how much available pressure capacity do you have when you are flowing water out of the hydrant? So NFBA 2 91. Doesn't have, uh, definition for flow test, but it does have some information in chapter four that speaks a little bit about the intent and the purpose of a flow.
4.1 0.1 states water flow tests are conducted to determine available water supply for fire protection purposes. The flow that would be available from a fire hydrant for firefighting purposes or the status of water supply distribution systems for fire protection systems or firefighting purposes evaluating the water supply.
For firefighting purposes or for fire suppression system purposes, there are different jurisdictional requirements, but 20 PSI is generally the lowest that you're allowed to test a hydrant flow test in order to determine adequate water supply. What I mean to say is. You're supposed to maintain at least 20 PSI for firefighting purposes.
So if you're getting readings of residual pressure that are below 20 PSI, there is a good chance that you are gonna have a problem. Moving on in chapter four, 4.3 says procedures. 4.3, one says Tesha be conducted during periods of peak demand based on knowledge of the water supply and engineering judgment.
So we want to conduct these flow tests during normal system usage and or peak system usage to. See how the system performs when there is, uh, the peak level of strain on the water supply so that we can provide a safety factor for our engineering calculations. Some jurisdictions will have additional criteria or reductions built into what they will allow you use for water supply data.
So some counties may. Uh, ask you to derate your water supply a certain fixed PSI number or a percentage of the overall water supply curve. So that's something to be aware of. Flo test is one of the preliminary steps for establishing fire protection systems for a facility. generally, this task is done by either the, um, engineer or the contractor.
And the purpose is to get a sense of if a sprinkler system is required for a building, or if you're trying to determine if you have adequate fire flow, if the system will be able to bear that flow and pressure, this required by these systems, why the flow test is so important is because, uh, Option of having a pump or even worse, a fire protection water storage tank and a project in which you did not plan for either of these to be in your facility can have huge issues and could potentially stop the job and prevent it from ever being constructed.
Fire pumps and fire protection, water storage tanks can be extremely cost prohibitive, hundreds of thousands of dollars to install these systems. And there are building programmatic elements that cannot be ignored. So if you have a project where people are, you know, um, not interested in getting a flow test, you need to, um, let them be aware what kind of risk and liability that they are taking on for the project and the problems that could be at hand later on in the project process.
Typically before you go out and do a flow test, you're going to take a look at the hydrants on the site and that are available to do the flow test. You, it's not uncommon to let the fire department know and to let the municipal water authority know, um, That you're gonna be doing a flow test so that they don't have alarms going off and you don't have, uh, a fire truck showing up on scene.
How many fire hydrants that you are going to flow? Depends largely on the system that you're gonna be tapping into. And the fire suppression demand that you are looking to utilize for your facility. generally, you want some broad picture of preliminary hydraulic calculations for your facility before you perform a hydrant flow test so that you can, uh, flow water near the system demand points that you are looking to utilize for the.
Generally, it's a very good idea to have a good picture of what the water supply system looks like around your facility. Um, if you're working with a, a base or somebody that, uh, a municipality that keeps a water map, you may be able to get this information from either the building owner or the municipal authority, having jurisdiction.
It's not just important that you do a flow test, but you also wanna be sure that the recommendations of NFPA 2 91 are considered. , it's not uncommon that if you ask somebody who is not used to doing flow tests, that they won't capture all the data points that are necessary or provide the right documentation for the results to be of much good use, depending on how many hydrants that you need to flow, which is based largely on your system demand and the capability of the public water service, you may need to flow more than one H.
For an aircraft hanger or another facility that has a very large system demand. You may be in a situation where you need to flow two or three hydrants. There are some interesting diagrams and figures in N FPA, 2 91 that show some example, layouts for flow tests, your flow hydrants, and your residual hydrant, and some of the water flow characteristics of what are going on during this kind of.
After the test is conducted and you have received your data points. You are going to plot your results on a water supply, uh, graph. That's it for this time. Thank you so much for listening. And we just scratched the surface on flow tests. I hope you enjoyed it, and we will see you next time on fire code tech.
Thanks for listening everybody. Be sure to share the episode with a friend, if you enjoyed it, don't forget that fire protection and life safety is serious business. The views and opinions expressed on this podcast are by no means a professional consultation or a codes and standards interpretation. Be sure to contact a licensed professional, if you are getting involved with fire protection and or life safety.
Thanks again. And we'll see you next time.