Last week, I wrote about why estimating the flow through a main drain is more complex than just calculating the resistance of one open orifice to how much flow comes out.

The problem with simply using an open orifice is that we calculated the maximum possible flow from that opening. That was what I wanted in order to hand off a maximum possible flow for a plumbing designer to accommodate, but the maximum calculation is problematic if we want to estimate how much actual flow comes from a main drain.

In last week's comments, we shared different ideas and models too (thank you!).

Essentially, at least in theory, the flow from the open end of a main drain is restricted at the opening but also throttled by the pipe path along the main drain (including the length of pipe, friction, and any obstructions), the main drain valve, and the parameters of the riser.

Additionally, our riser gauge measures the normal pressure even when water flows. It's not a pitot gauge.

Considering that, I took the conceptual outline from last week and built an iterative tool that takes all the input information we need and estimates flow from a main drain.

What this does is take the main drain configuration, take the main drain residual pressure we get, assumes and loops a pressure balance, and turns out a theoretical flow from the main drain.

The caution here is that this is an estimation, and we haven't proven what input values are most-accurate from real-world tests. For instance - how much of the pipe is obstructed, on average? What c-factor best represents real-world conditions? What would an error analysis suggest about our range of possible flow?

All these can be tested and figured out in time, but in the meantime I wanted to offer up the first draft of the tool for your exploration and feedback:

Give it a spin, and let me know what you think.

If you find a bug, let me know and we can discuss improvements in the comments.

Thanks as always for being part of our community here! Hope you like this one.

​- Joe

One of the curiosities I have every time I run a main drain or see one run is how much flow the system is actually discharging.

From the amount of discussion and inquiries one of our tools has generated, I know many of you are curious about it, too.
 
HOW MUCH DOES THE MAIN DRAIN ACTUALLY FLOW?
For one – if we knew with some certainty how much flow came through the main drain, then we could actually complete a backflow forward-flow test entirely just by opening up the main drain all the way.

That’s the theory, at least, that I’ve heard some people point to as to why they don’t provide another fixed means of forward flow.

For a lower hazard system; say a system whose greatest challenge is still Light Hazard – it’s not unfathomable that a fully-open 2-inch main drain could flow at least the system demand (which might be as low as 120 gpm for a minimum quick response (QR) reduction area and 30% overage, no hose allowance included).

Even for an Ordinary Hazard Group 2 system using a QR area reduction and 30% overage, the system flow may still be in the 220-250 gpm range. Would a fully open 2-inch main drain be enough to handle it?
​
Or what if that main drain was upsized to 2-1/2 inches?
 
This piques the curiosity, right?
 
IS FORWARD-FLOW ACHIEVABLE THROUGH A MAIN DRAIN? IF SO, WHEN?
It would be very nice to have an idea if forward flow was achievable for some of these lighter-weight systems just through the main drain.
 
The Drain Flow Estimator

We introduced a tool we called the Drain Flow Estimator tool a while back (https://www.meyerfire.com/blog/a-new-fire-sprinkler-test-drain-flow-calculator), which was built to estimate the maximum possible flow from an inspector’s test or a main drain.

That tool only uses one calculation: discharging water through an open orifice:

Let’s say we have a very large water storage tank and poke a hole in the side of it near the bottom. How fast does water drain from the tank?

We have a formula for that. It’s Q = 29.84 C d^2 √p.

That is, we have a flow (gpm) that is constrained by the type of opening (C, the discharge coefficient), the diameter of the opening (d, in inches), and the total system pressure at the opening (p).

​We use this regularly when we conduct fire hydrant flow tests. The equation translates pitot pressure to how much flow comes out of the opening. We took measurement inaccuracy into account and built this out into its complete tool for converting pitot pressures to flows (https://www.meyerfire.com/blog/new-pitot-to-flow-rate-converter-with-precision).

THE PROBLEM
​Here’s the problem with using only that equation to estimate flow from a main drain – it’s the maximum possible flow.
​
Now, it meets the need that we had for building the tool—to estimate the maximum possible flow so that we could size drains appropriately (hint: don’t run an inspector’s test or main drain to a janitor’s sink).

It serves its purpose of estimating the maximum possible flow.

However, the Drain Flow Estimator tool doesn’t provide a realistic amount of flow through the main drain or inspector’s test and drain, only the maximum.

That’s problematic if we want to know the actual flow through a Test and Drain or a Main Drain, as discussed earlier.

Why is it the maximum and not actual?

#1 PIPE CONSTRICTION
That is, we’re not accounting for the pipe's constriction between the opening and the riser, the friction loss within the riser itself, the loss through the elbows along that path, or the constriction at the valve opening.

#2 TYPE OF PRESSURE
Another thing we’re not really considering is the type of pressure that’s measured. When we take a pitot pressure measurement, we insert a tube into the centerline of the water flow.

The pressure measurement taken from a pitot gauge accounts for the static pressure of the water (the normal pressure that is exerted in all directions) and the velocity pressure caused by the forward motion of the water.

​That’s what a pitot gauge is measuring—the total pressure.

​A gauge on a riser does not measure total pressure; it measures normal pressure. That is, it doesn’t matter if the water is standing still or moving at 20 feet per second. The gauge is only measuring the pressure that runs perpendicular to the pipe in the normal direction.

#3 LOCATION OF PRESSURE
The last source of error is where the pressure is measured.

For a hydrant flow test, we measure the pitot pressure immediately after the hydrant opening. We use the formula and convert it to a flow, knowing the pressure right at that opening.

If we instead use this same formula for an open orifice but add a pressure upstream at the riser, then we’re using a higher pressure than what will be available downstream at the opening of the main drain.

If we want to know the maximum possible flow, that’s probably fine. That’s the extreme case.

But if we want to know the actual flow through the drain, then that’s problematic; it’s another source of error.
 
BUILD A TOOL THAT CAPTURES ACTUAL?
So, how would we construct a tool that estimates the actual flow through a main drain?

Well, in theory, we could work an iterative loop like this:

1. Assume a pitot pressure right at the opening of the main drain (the 45-degree elbow discharging to the outside, for instance).
2. Translate the pitot pressure to a flow based on the characteristics of the opening.
3. Knowing the flow through the opening, we could calculate the friction loss as we move upstream through the main drain.
   1. We will gain pressure as we move upstream, just as in a hydraulic calculation.
   2. This would require an estimated C-factor for the pipe, knowledge of how the main drain is routed, and information about the pressure loss at a main drain valve.
4. At the point where the drain connects to the riser, we could determine the pressure at that intersection, and we still know the flow.
5. We calculate the friction loss going upstream through the riser until we reach the riser pressure gauge.
   1. We would need to have an estimated C-Factor for the pipe and know the routing of the riser.
6. Now, we would have a total pressure where the gauge is located.
7. We also know the velocity of the water movement in the riser, which we can use to translate our total pressure into the normal pressure, which is what the gauge is reading.
8. We would compare the estimated normal pressure calculated to the actual normal pressure in our real-world test.
   1. If our estimated pressure at the riser is too high, we restart our loop and assume a lower initial pitot pressure.
   2. If our estimated pressure at the riser is too low, we restart our loop and assume a higher initial pitot pressure.
9. We iterate this loop until we’re close enough for our needed accuracy.

 
As a result of this process, we would have an iterated, balanced supply-side hydraulic calculation that estimates the flow coming through the main drain.
 
If you love the math or the theoretical exercise – weigh in on your take. Open to ideas on this.

DOWNSIDE & POTENTIAL MISUSE
Now that’s great Joe, so go ahead and build it (typed in sarcastic voice font).

We can build it (and probably will because I’m curious). If we do, I’d want to go out to a parking lot and validate this in the real world 30 different ways (looking at you Fire Sprinkler Podcast).

But beyond that, there’s a fundamental issue with a calculator like this – it’s still an estimated amount of flow based on a pressure measurement at the riser but with the flow coming out downstream some distance later.

AN ESTIMATE BUT NOT REALITY
It’s not a measure of the actual flow through the opening; it’s only a calculated estimate.

The downside of not being a measurement is that if there’s some wrong assumption—say a C-factor or number of elbows or whatnot—then we introduce inaccuracy.

But it's probably hard to detect. What if we have some type of pipe constriction that we can’t see from the outside? Say there’s a large rock or dirt buildup, or the coupon that was cut for the main drain tap is actually smaller than it should be.

That constriction would throttle the actual flow down but maintain the same or higher pressure upstream at the gauge.

That is – it would look like it’s flowing more water than it actually is.

The advantage of measuring the actual flow out of a main drain is that we know with some certainty what the flow is achieving and not an estimate.

Fundamentally, I know of two quick(er) ways to measure the flow, even for a main drain.

There’s the bucket test, in which you flow into a large 55-gallon drum and time how long it takes to fill it up. Divide your bucket size by the time it takes to fill up, and you then have your average flow.
​

​Then there’s the pitot measurement. Connect a test hose with an adapter to the main drain, measure the pitot pressure, and convert it to a flow.

​Either way, you could measure the flow coming from the opening. That’s far more accurate, of course, than a tool that estimates and incorporates a handful of assumptions.
 
THE UTILITY?
Is this kind of tool, that provides a theoretical balanced supply-side flow with the supporting math and documentation, something that would be of interest?

Do you see the harm in having an estimate doing more harm than good here?

Do you ever use a main drain for forward flow on less hazardous systems, and if so, do you verify what that flow is?

Curious on your thoughts about this as a challenge in the lens of trying to create helpful resources and not circumvent or obstruct good practices.

As always, appreciate you being here and being part of the community.

​- Joe

Have you specified or encountered a specification that asks for the pipe to be "as high as possible" in areas with exposed structure?

If so, does that mean we want to pipe through the open web of a structural joist?

THEORY VERSUS REAL-WORLD
This might be the most classic design versus real-world installation conundrum. Just because something might be possible doesn't necessarily mean it will fit. 

Well, for some years now, I've asked people I respect how they determine whether a pipe can go into the joist.

SHOULD WE ROUTE IN OPEN WEB JOISTS?
We might first want to ask whether we should put the pipe in the open web joist, to begin with.

If the joists are shallow, not going to be aligned, or will they be interrupted by solid beams and the end of each bay? In those cases, then the pipe really shouldn't be up there anyway.

But, assuming we do have some depth to open-web joists, and the joists will be aligned (giving us an open and continuous path to hang the pipe), we still need to know if the pipe will fit.

LENGTH OF PIPE THAT WILL FIT
The answer from an novice consultant might be - well of course it'll fit. Just cut the length of the pipe down so that it'll fit up there.

But where do we draw that line? If we have hundreds of feet of pipe run in an open-structure area, it's going to be a labor and materials nightmare if we have to use 6-ft long sticks of pipe the whole way down. Additional fittings, additional hangers (if we want a hanger on each stick of pipe), additional labor... major cost impact.

If we can use cut lengths of 10'-6" (half of a full-length 21-ft stick of pipe), then maybe that cost impact isn't as bad.

CALCULATED APPROACHES
In asking around, I've found three different calculated methods of determining whether a pipe will fit (mathematically) to slip up and into open web joists.

Those three methods, as I can best identify, is a calculated simple method using exponential relationships of the joist depth and gap-between joists (I called it the Simplified Formula, please inform me of a source if you know it). This is the second calculation.

The third was originally credited to AFSA's Ed Miller from the 1990's, which I've identified third in the list and seems to generally be the most-conservative of the three calculated concepts.

And the main concept is a purely diagrammatical calculated approach based on the visual. The concept is that the slope of the pipe just as it slips past the joist on the right is calculated, the rise of the pipe is calculated and compared against the available open height in the space (can the height of the left-end of the pipe fit underneath an upper-chord?).

SKETCHED APPROACH
Of course, we can always draft or model up an example and see it for ourselves, but my hope in creating this tool is to shed some light on the practicality of putting pipe up into the joists and help see that relationship come together.

​Below is the tool:

TOOLKIT
If you like tools like this - you should check out our Toolkit and MeyerFire University (which includes the Toolkit). Plenty more practical tools for everyday use for the fire protection professional.

YOUR TAKE
Where do you land on this?

Have you used any of these methods before, or do you have your own?

Do you know where these originated, and if so, point me in the right direction so I can credit the right source?

​Comment below - would love to know your thoughts on the topic and where you see something like this helping.

This week we have progress and are continuing the effort to create an open, easy-to-edit and easy-to-digest basic sprinkler specification.

The first week we touched on the need and developed the general criteria. Last week we expanded on the feedback and introduced equipment to the spec.

This week we’ve adapted the specification based on feedback from you (thank you!) and are adding in the ‘means’ portion of the specification.

THE GOAL OF A SPEC
Our goal here is to have a simple baseline specification that answers the most critical questions which a specification should resolve, and otherwise stay out of the way. A great specification should:

• Be clear, unambiguous, and concise
• Address key questions for the scope of work
• Be clear about owner expectations that exceed code minimum
• Not include redundant, extra, unenforceable, or extraneous information

OUR INTENT
This specification is not intended to replace consultant’s own customized specifications that are well thought out, intentional, relevant, and updated.

They are intended to be a free, easy-access alternative to stand in for specifications that are boilerplate, don’t answer critical questions, or haven’t been updated in twenty years.
 
Based on your feedback, this week’s updates include references to water storage tank, using an imperative tone, cleaning up portions of the system, adding standpipe and dry system references, and incorporating your comments.

Don't forget to comment below on the questions we posed. I am very grateful for your input and willingness to push the industry ahead, as always!

​- Joe

Last week I worked error propagation for a pitot measurement to flow rate conversion.

Because it's a measurement, there is a natural level of precision that we can only estimate that depends on the precision level of each of our measuring points (our tools).

Yet, we (maybe just I) often overlooked the concept of measurement error. In this tool (below), I've incorporated the error propagation to suggest a range for the result instead of what we typically express as a near-certain test measurement.

So, now, you can convert a pitot pressure into a flow rate and immediately get the error tolerance based on the tools you've used and measurements you've taken. Hardly any additional work.

While it may sound trivial, knowing what amount of tolerance we are actually achieving in a test measurement could be the difference between a test pass or test failure - especially in regards to fire pump testing.

Check out the tool below, and let me know what you think! It has an IP and SI version built in (I'm finally catching on).

If you're a member of MeyerFire University this will be added to the iOS and Android app automatically. 

Thanks and have a great rest of your week!

​- Joe

This week I'm happy to debut an update to one of our popular tools, the K-Factor selector, which is a part of the Toolkit. 

This tool quickly calculates the actual pressure and flow across different types of sprinklers. It's helpful when we're trying to select the best-possible sprinkler for a hazard. 

Even for light hazard areas, a standard k5.6 sprinkler may not be the 'optimal' sprinkler, from a hydraulic perspective. We touched on this when looking at whether the flow through a sprinkler is governed by the density and area or by the k-factor and minimum pressure.

In short, the minimum flow through a sprinkler can be driven by the coverage area of the sprinkler multiplied by the density of the hazard, or, it can be driven by the k-factor of the sprinkler and the minimum pressure that sprinkler requires. 

In either case, it's important to make a quality selection for the k-factor if we want to reduce the required pressure and flow that a system will demand. Less flow usually means less friction loss, which can result in more efficient systems and smaller pipe sizes (saved cost of material and labor). 

The updates to this tool make it mobile and tablet friendly, and also now clearly indicate what the 'optimal' sprinkler k-factor is for flow and for pressure (hint: they're not always the same). If you're a Toolkit user, just click the image above to see the updates. Thanks!

It's been too long since our last cheatsheet! Happy to bring about a new one to the table today. 

One number that I seem to always need to crunch when laying out or reviewing fire sprinkler systems is the remote area adjustments, and the minimum width of a remote area. This applies specifically to the Density/Area method of Hydraulic Calculations in NFPA 13.

The formula is simple enough, w = 1.2 x sqrt(remote area size), where w is the minimum remote area width, and the remote area size is our final adjusted remote area that we're using.

Now for a routine calculation with a remote area of 1,500 sqft, I pretty much have the 46.5-foot area width memorized. Why is it important? The minimum width dimension tells us how wide our remote area needs to be. It's the dimension parallel to the branch lines, that captures as many sprinklers as it can along the branch line. 

We take this minimum area, see how many sprinklers this area covers, and round up to the next whole sprinkler. It's our minimum width dimension that we're not allowed to reduce.

The 46.5-foot dimension might be easy enough to remember, but what about when a remote area is reduced using the quick-response reduction? What if the ceiling is also sloped? 

Adjustments to the remote area are a process on their own, and each have implications for the minimum remote area width.

If you're using our Toolkit you already know we have tools that will compound the calculations for you. Our Quick-Response Reduction tool will adjust the remote area size based on the ceiling height, and our System Estimator tool will adjust for quick-response, sloped ceilings, dry and pre-action systems, high-temperature sprinklers, and more:
​

But, there are still times where I just want to quickly glance at my remote area size and translate that into a minimum width. That's what today's cheatsheet is all about.

​This quick reference PDF helps address a few things: 

• You can quickly see the adjustments for quick-response sprinklers, based on the maximum ceiling area.
• You can see cumulative adjustments, like multiple 30% increases or quick-response reductions on sloped ceilings
• You can quickly translate a remote area size to the minimum remote area width that is required.

I hope this one is helpful for you as conduct or review hydraulic calculations on your projects. Any tips, feedback or improvement ideas, be sure to let me know. 
​
Thanks & have a great rest of your week!

​Today is a pretty big day in MeyerFire-world. 

I've spoken with contractors, consultants, plan reviewers, educators, insurance carriers, installers, inspectors - and we all continue to come back to one big issue that is holding our industry back right now.

We need to develop new talent. 

For the organizations that are busy and growing - we need more help, and we need knowledgeable help.

When we look out even a little into the future, even just 2-5 years from now, the problem will be compounded. Call it the Silver Tsunami, the Experience Exodus, the Golden Goodbye, or whatever other name the kids come up with - our industry has already lost a lot of experience to retirement, and that will only continue as many of the remaining Baby Boomers look to complete their careers.

We need to develop new talent.

We need something that can resonate with today's Gen Z. We need engagement, and a way to not just train in a two-day or two-week sprint, we need something that can help people new to the industry learn every single day, year-round.

Around here we've thought and debated and circled on the idea for a solid couple years. 

I'm excited to say that we finally have the platform that we have built specifically to help develop new talent in the fire protection industry.

We're calling it MeyerFire University:

​​It's an all-new training platform built for those with 0-3 years experience, and covers technical topics like fire suppression, fire alarm, code, life safety, and specialized systems; it covers production topics like plan preparation, drafting, modeling, and plan review; and it covers business & career topics as well.

It's everything we wish we had when we started, delivered in bite-sized, highly-visual video clips that are delivered daily and on-demand.

Today is our "Soft-Launch". 

If your organization finds that you also have this need to help train and develop new talent - and you want to join in on this platform early - now is a good time to do so.

We've only been in full production on our video content for a month and our platform is growing by five new video modules each week. If you're wanting to be an early adopter - we have a couple ways of saying thank-you and making sure the platform is worth your team's time.

To get a quote & more information for your organization, visit:

​This has been a dream we've worked towards for years now, and I'm thrilled that it's finally coming to light and can soon start helping teams like yours shine.

Thanks for your time and being a part of the community for better fire protection!

It's been something that has been requested here and there about the Toolkit, and I'm happy to say we've finally come around and made this happen. I apologize that its taken way too long to get some of this training out.

If you're a Toolkit user (thank you!), we now have a welcome series of weekly emails that explores each tool in a little more depth. Some emails are articles exploring some of the topics, some emails include videos explaining the tools in a little more detail. You can always unsubscribe at any time.

To sign up for this free email series, you can do so here:

If you don't already have our whole set of tools, check it out here: www.meyerfire.com/toolkit. Happy to say it continues to do well thanks to your feedback and referrals! 

That's all for today - thanks and have a great rest of your week!

The fire sprinkler database is coming up on its third year in existence; it originally took hundreds of hours of research and plenty of updates, but we're happy to say now that we've upgraded the database to include better search, sort and filter capabilities. 

The database is a collection of over 1,500 fire sprinkler models on the market today. Even with a select number of manufacturers, finding just the right type of sprinkler with correct spacing and minimal pressure demands can be tough. The database was built to get answers in seconds - with links directly to manufacturer websites & data sheets.

See a quick update video here:

​The database is part of our Toolkit package. More information about that here.

Have a great rest of your week!