New Hose Valve Requirement for Forward-Flow

Last week we updated the NFPA 13 shop drawing checklist with references to NFPA 13 2019 and 2022 Editions.
 
While code updates like this are traditionally modest, the NFPA 13 Committee revamped the entire list of requirements for “working drawings” in the 2022 Edition. It was gutted.
 
We’ll expand on that more next week.
 
This week I’d like to key in on one very impactful change that I think will affect many of us in how we design systems going forward.
 
FORWARD-FLOW REQUIREMENT HISTORY 
A forward-flow test has long been required in NFPA 25 (dating back to at least 2002).
 
The purpose of the test is to verify that a backflow preventer is capable of fully-opening in a fire – or at least to the extent that it allows enough water to flow to satisfy the sprinkler system’s demand.
 
A means of conducting a forward-flow test has long been required, but not necessarily readily implemented. For many lower-hazard systems, it was a test that was possible by flowing out of a fire department connection or main drain.
 
WHY NOT FLOW OUT THE FDC?
White it was possible to do a forward flow through an FDC, this approach was never practical. I can’t stand on a high horse here – it was the approach I long used from a design perspective.
 
It’s not practical because conducting a forward-flow test out of an FDC would typically require a system to be shut off, drained, check valve reversed, put back into service, tested, shut off, drained, check valve put back into place, and put back into service. And that was if the clappers on the FDC were removed or restrained in a way to allow enough water to pass through. It’s a tall ask.
 
USE THE MAIN DRAIN?
Flowing out the main drain could be a solution for forward flow, but practically speaking how much water can flow through a 2-inch main drain, especially if there’s an OH1 or OH2 demand? Do we have a way to verify how much water we’re flowing, so that we know the test passed?
 
Some have used our own calculator to estimate the amount of water flowing through a main drain by using this orifice flow calculator - https://www.meyerfire.com/blog/a-new-fire-sprinkler-test-drain-flow-calculator
 
That calculation is based on pressure flowing through an opening – either an orifice or pipe diameter – and doesn’t incorporate the losses that occur through the length of a main drain or the fittings along the way. It’s going to be too generous on the amount of flow coming through a main drain – which is good if we’re wanting to know how much water a plumbing drain needs to accept – but bad if we’re trying to prove forward flow based on it.
 
I would suspect that a supply-side calculation (where the available pressure dictates the flow) through a fully-open main drain would be the best way to predict hydraulically how much flow a main drain could flow. If that’s well above the system demand (including hose allowance), then a main drain could be the means to flow.
 
But a 2-inch main drain is very likely not an answer for forward flow for most systems.
 
I’ll leave that discussion open – perhaps there’s a tool we could construct to account for main drain losses and perform that supply-side calculation.
 
PERMANENT MEANS FOR FORWARD-FLOW
Somewhat fortunately for those of us who like black and white guidance (myself included) –the NFPA 13 committee closed up the gray area in the 2019 Edition by requiring that an arrangement for conducting the forward flow test, at the minimum flow rate of the system demand (including hose allowance), would be provided “without requiring the owner to modify the system to perform the test.”
 
This comes from NFPA 13-2019 Section 16.14.5.1.1.
 
In the 2022 Edition, the committee went further.

A fixed means of forward flow, like hose valves on a test header or system riser, will become far more commonplace once the 2019 and 2022 Editions of NFPA 13 are adopted and enforced.
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A 2-1/2” HOSE CONNECTION FOR EVERY 250 GPM 
A test connection is now required for forward flow tests, where now a 2-1/2” hose valve is required for every 250 gpm (950 L/min) of system demand. This total flow must include the hose allowance where applicable. Generally, if there are interior hose valves, then this would need to get added in.
 
So - an Ordinary Hazard Group I system that may have a demand of 270 gpm (with 250 gpm outside hose allowance), would still need two 2-1/2” hose valves for the forward flow test fixed in place downstream of the backflow preventer.

For larger systems, or those with interior hose connections? We could be looking at three or more hose connections just for forward flow. This comes from NFPA 13-2022 Section 16.14.5.1.1. That’s a noteworthy change.
 
For a code-minimum, sprinkler-system-only type of project, that’s a tangibly different cost and look to a part of the system.
 
Does this have to be a test header on the outside of the building? Not necessarily, though that would be nice for future testing.
 
Could the hose valves be on a riser in a room that has exterior access? Depending on the room and goals for the building – that could be reasonable.
 
There are two provisional sections that allow existing hose connections to be used for the test (16.14.5.1.2), and other means to test are allowed “as long as the system doesn’t require modification to perform the test and is sized to meet the system demand.” The later comes from NFPA 13-2022 16.14.5.1.3.
 

Is a fixed test-header on the exterior of the building required?
No, but it could be convenient for future testing in areas where theft is less of a concern.
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HAVING TEETH 
But in general – we don’t have a “use the FDC” workaround any longer.
 
For those in IT&M, we finally have a sticking point to give an ability to do this test without tinkering with the system.
 
For those in design, we finally have a magic section of code that we can show to justify providing a means of the forward flow test.
 
For those in review and inspection, we have the teeth to enforce it.
 
Hopefully, in the long-run, having systems tested for forward flow will identify backflow preventers aren’t functioning and we no longer have them in buildings ready to fail when a fire happens.
 
Hopefully, this pushes buildings to a bit safer and helps us a be a little more confident in the system’s ability to fight a fire.
 
SHOW ON WORKING DRAWINGS
While the means is an installation question – NFPA 13-2022 Section 28.1.3(18) requires that working drawings locate and identify the means of forward flow.
 
It’s no longer a “how do you plan to do this test?” type of comment and will soon be “show the location and label the means of forward flow, per 28.1.3(18).”
 
MY FORWARD-FLOW STORY
Are we really just testing the backflow preventer here?
 
Well, yes. In part.
 
But actually flowing an entire system demand tells us quite a bit. It means that our water supply is capable of flowing the full system demand, and all the pipe in-between the water supply and the backflow is also open-enough to flow the full system demand.
 
I once had a project where a tap was made to the city supply main. It was a live tap or “hot tap,” where a drill punctured the side of the city main and a new 6” street valve was installed and our 6” underground came in and fed the building.
 
It was a brand-new 3-story building that was going to have overnight guests.
 
The tap wasn’t fully-made. In fact, as we found out later through a lot of cost and trouble, only a ¾” pilot drill bit made it through the city main. It wasn’t all the way drilled-in.
 
Instead of a 6” tap, we had a ¾” tap.
 
Static pressure to the building was fine.
 
We could run a main drain test just fine (the residual dropped, but the main drain isn’t flowing all that much). Remember – the initial main drain test sets the threshold to check against in the future.
 
We could flow the inspector’s test just fine.
 
When we conducted the forward flow test and opened a couple 2-1/2” hoses – we had no water. No pressure at all.
 
It wasn’t until we conducted the Forward Flow test that we knew there was a problem.
 
Where it not for the Forward Flow test, we would have had a brand-new building, which, by all other measures we would have thought was designed and installed properly – all protected by a system with water that was squeezed through a ¾” hole.
 
While the backstory of testing the Forward Flow may be more about the backflow preventer, the test does give us confidence in the supply up through the backflow preventer being able to handle the system demand.
 
If we measure the flow coming from the forward flow, and also stick calibrated gauges on the upstream cock and downstream cock of the backflow – we can know a whole lot about the health of our system that day.
 
What’s the static pressure? What’s the loss through the backflow? What’s the base of riser pressure at the system demand? How does that compare to our design?
 
We can get a lot of information just from this one test.
 
END SOAPBOX
That’s my soapbox rant for today. As with all we write and do on this site, I hope you’ve found it helpful.
 
Keep fighting the good fight, and have a great rest of your week.
 
- Joe ​