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 posted the start of an open specification and asked for feedback - and boy did you all not disappoint!

If you haven't read that post, it's where to start. We laid out a few ground rules about what we're trying to achieve.

I genuinely appreciate the review, the comments, and the emails. I'm very encouraged by what we'll be able to build together that can improve things for all of us.

Who knew putting together specifications could be so fun? Joking - sort of.

As you're able to skim through this updated draft, which now includes Part 1 (General) and Part 2 (Products), here are some of the areas worth paying attention in a little more detail:

#1 - CHANGED SECTION NUMBER
We've updated the specification section number to reflect that this isn't just a wet-pipe specification; it's intended to consolidate many pages of redundancy into our main goal; a concise, easy-to-read and easy-to-edit specification.

#2 - NOTE TO NOT FALL BELOW CODE MINIMUM
There's a line added under C in the "1.1 DESCRIPTION OF WORK" that reads "at no time shall work be less than the applicable codes and standards listed below. Proposed alternatives, discrepancies, or questions shall be addressed by written Request for Information."

My goal here is twofold; one is that we're protecting the consultant and enabling the contractor to push back in written form. 

At the end of the day, we need a code-compliant system. The days of turning a cheek or intentionally being above code because a PE said so should be over. 

The concept with this inclusion in the specification is that if the contractor sees something (anywhere) that is less than code, then they have an avenue to have it addressed formally and an opportunity to clean it up in the project.

On the opposite side, the consultant has some relief in that they're clearly not advocating or instructing the contractor to fall below code unless it's in approved written process (such as an approved code-alternative).

I hope this to be a win-win opportunity for code-compliance at the end of the day. Like the others - curious on your take.

#3 - OPTION FOR PROFESSIONAL ENGINEER TO BE AN FPE OR "KNOWLEDGEABLE AND EXPERIENCED" IN FIRE PROTECTION
There's a tangible value to being a Fire Protection Engineer (informally an "FPE") specifically. An over-generalization would be that the Engineer has taken the time to study and pass the Fire Protection P.E. Exam, which itself is no small feat. 

With that effort and focus (which often takes months of preparation even for seasoned Engineers) there's a line in the sand that speaks to that individual 'owning' fire protection as a key area of focus and effort. 

Being an Engineer who passed the Fire Protection P.E. Exam doesn't make someone more knowledgeable (outside of learning many new facets while studying) nor better than another Engineer, but it does reflect a certain level of dedication to the fire protection field specifically.

That said, we as an industry have far fewer Fire Protection Engineers than Professional Engineers in other disciplines (my at least an order of 10-to-1), so mandating that all shop drawings be performed by or under the purview of a Fire Protection Engineer can be impractical.

It's a bigger discussion point for sure, but I've modified the specifications to either call for an FPE specifically, or to mandate a Registered Professional Engineer "who is knowledgeable and has experience in the field of Fire Protection."

I'd be curious on your take with this as well.

#4 - MOVED QUALIFICATIONS TO 1.5 QUALITY ASSURANCE
More of a practical shift here, we had a few requests to move the licensing and qualifications to the Quality Assurance section in 1.5 and out of the Submittal section of 1.4. Seems to make more sense here.

#5 - ADDED PART 2 FOR PRODUCTS
Since last week we've also drafted Part 2 where we cover Products. This should add a little more 'meat on the bone' and probably queue up plenty of contention points. 

Let me know what you like and what specifically you would change - all for building a better industry. Click below to view, and thank in advance for helping bring to life a needed resource!

One of the frustrating aspects of bidding a fire sprinkler job in North America is when you're reviewing a job and the specifications that accompany it are simply terrible - boilerplate, don't actually provide any useful information, are conflicting, include irrelevant content, or clearly haven't been updated in decades (list no longer manufactured products).

One of the ideas we kicked around a couple weeks ago was essentially an "open source" specification. One that we build and curate together and post for open use.

This is the first-stab at what "Part I" of an open, basic fire sprinkler specification might look like.

SECTION I OF THREE
Typical specifications include three parts:

1. Conditions: where the scope is described, applicable criteria is communicated, and the 'what is supposed to be done' is addressed.
2. Equipment: what equipment and products are permitted, and what are not.
3. Execution: in what ways must the work be performed.

OUR GOAL
From our collaborations, posts and discussions thus far, we're all really wanting something that is:

1. Helpful: actually provides information the contractor is needing to price a job.
2. Concise: as short as possible, so that it's easier to read and easier to edit. Don't duplicate requirements from other standards (such as NFPA 13), but simply defer back to them. We also want to limit the number of sections (again for simplicity, easy to navigate).
3. Clear: the specifications need to be easy to navigate and explicit in what is being required.
4. Timely: we don't want antiquated methods or products that aren't feasible or achievable.

There are other goals too, but those seem to be the reoccurring themes.

We explicitly do not intend for this specification to replace consultant's who already update and care for the industry. The beauty of consulting is providing unique value to your clients - this is absolutely not intended to be the only specification available. 

Rather, we would hope that it could help provide a baseline open-source template where specifications could at least be of this quality level.

YOUR INPUT
Where we could really use help here is reviewing this initial (very very first) attempt at Part I a basic open spec. 

I have highlighted GREEN and BLUE areas where a specific selection needs to be made (one or the other).

I have highlighted YELLOW additional alternatives which may be less common than a typical, mid-size commercial job.

​All portions of this specification would be editable, though the highlighted areas would be of particular concern to change and update job-to-job.

Take a look, and let us know your thoughts. If you've been long-frustrated about the prevalence of terrible specifications - then this just might be your opportunity to help us clean up the practice:

Part II, which comes next, identifies equipment and products that are allowed or not.

Part III speaks to the execution of the work - that is, any restrictions on what needs to be achieved.

THANK YOU
Just want to say a big thank you in advance for helping us really impact the industry in a positive way. I and many others very much appreciate it!

​- Joe

HOW DO WE FIX BAD SPECIFICATIONS?
Last week I touched on a concept of using large language models to instantly review a series of specifications.
Thanks for the comments! I’ll write up the step-by-step and incorporate that in a how-to video for posting here and on YouTube.

A special shout out to Kimberly Olivas, Brian Gerdwagen and Casey Milhorn on their comments in that thread – very helpful and insightful.

The discussion brings me back to two questions I may have inadvertently skipped right over –

1. Do we, as an industry, want to fix bad specifications?
2. If we do, and Pre-Bid RFIs are a luxury of the past, then what is the best way to go about improving bad specifications?

A PROBLEM WE CARE TO FIX?
If part of a bidding contractor’s value proposition is using their expertise to sort through bad specifications and give an advantage; either in exclusions or clarifications, or change orders later in the process due to inaccuracies, scope not meeting code, or scope gaps.

In other words, based on a bidding contractor’s position – there might not be any incentive for them to play their cards for competitors to see through the Pre-Bid RFI process other than a smoother project experience for the owner.

A bidding contractor is not a representative of the owner; the consultant is. Ultimately the consultant is responsible for protecting and supporting the owner – which is why they were hired in the first place.

Perhaps many contractors don’t look at it that bluntly – but I can understand the sentiment not to tip a hand at project issues when it could mean losing a bid.

WHAT’S THE ANSWER?
If Pre-Bid RFIs are not the cure-all in today’s pace of estimating – and contractors are not incentivized to be correcting consultant issues – then do we care to actually fix it?

For estimators – are bad specifications purely an annoyance for you – or do they cause issues on your projects?

Would you prefer that specifications actually be well written?

I’m not being facetious – I’d love to know your take on this.

ALTERNATIVE APPROACHES
If better specifications (and plans) are something we deem better for the industry – and we collectively want better plans and specifications – what is the approach to get there?

More specifically, how do we encourage those who don’t really care about fire protection to put a little more effort into their plans and specifications?

This was last week’s idea:

• Use AI (ChatGPT or other) to instantly review specifications for contractors to submit Pre-Bid RFIs that clarify the scope

Here are some alternative from-the-hip ideas that I’d love to kick around with you and see if you find any of these might be viable:

IDEA #1: PUBLISH AN OPEN MICROSOFT WORD FILE BASIC FIRE PROTECTION SPECIFICATION

• Community-created/reviewed
• Easy to read, easy to edit
• Free/Open
• Benefits: easy to access, eliminates excuse for costly specification programs
• Drawbacks: apathy (those who don’t care may still not use freely-accessible content)

IDEA #2: CREATE AN AI TOOL FOR CONSULTANTS TO QC THEIR OWN SPECIFICATIONS

• Basically an AI quality-control tool
• Free or low-cost
• Benefits: fast, easy to use
• Drawbacks: would be mostly mechanical in nature – AI wouldn’t be good at discerning scope compared to plans or the rest of the project. Also, apathy (see above).

IDEA #3: PROMOTE OR CREATE A LOW-COST SPECIFICATION GENERATOR

• Even easier to edit
• Low cost
• Uses today’s products and quickly generates an editable format
• Benefits: fast, easy to use, requires little effort
• Drawbacks: some cost involved

IDEA #4: HAVE A FORMAL THIRD-PARTY REVIEW PROCESS (A GROUP) FOR SPECIFICATIONS

• Real people (estimators and/or manufacturers) who would do reviews of specifications for improvements to a specification template
• Would be more of a ‘one-time’ review process, not project-specific
• Could involve NDAs to protect consultant’s work
• Benefits: real people helping improve templates overall. Would be an easy-to-access and formalized way of having multiple parties review specifications to improve overall quality. Real people helping real people.
• Drawbacks: requires time, labor, and possibly some cost - depending on the demand.

IDEA #5: PUBLIC HUMILIATION

• Going from a human-positive to human-negative approach: simply collect and post examples of bad documents/specifications in a way for everyone to learn from (but without identifying the people or companies that created them).
• Benefits: it may actually encourage real action
• Drawbacks: not fun, not an industry-building environment, can get negative quickly

IDEA #6: YOUR IDEAS

• What’s your take? How would you improve the process? What do you like or not like?

 
Do you (1) think this is a problem that should be fixed, and (2) what concepts do you think could make a difference?
 
Comment below – would love to foster a deeper discussion on how we might solve this problem before skipping ahead and creating something that might not be impactful.

One of the things that frustrates me to no end about our industry are bad specifications.

If you want to skip the story and dive right to the end – my ask today is that you comment below on what you would want an automated tool to check for when it reviews a set of specifications?

In other words, what issues have you found in specifications in the past that you would want an ideal tool to check for?

I’M GUILTY, TOO
Before I dive deeper and sound preachy, I have two disclaimers:

1. I am not above making poor specifications and I’m confident that I’ve issued bad specifications as a consultant – so I’m absolutely not above the violators I harp on here - and
2. If you are a consultant and care about the quality of your work output (true quality – as in doing quality work that helps foster a smooth project) – let me be clear that this is not directed at you. If you care to improve your work quality over time, you’re clearly not in the camp that I’m talking about today. The bad offenders, honestly, don't care - and it shows in their work.

WHAT MAKES A BAD SPECIFICATION?
What makes a bad fire protection specification?

The most dangerous is probably direction which would not meet code minimum. Ambiguity or conflicting information makes bidding difficult. Mandating things which don’t exist for the rest of the industry (such as velocity limitations in hydraulic calculations) can be unnerving and increase cost unnecessarily. Some of the most obvious parts of a bad specification are mandates for products or manufacturers that no longer exist.

The goal of a good specification is the same as the plans – clear, unambiguous communication of what is included and not included in a scope of work.

LITTLE RECOURSE
After a project is awarded, a contractor naturally has very little leverage to change the scope of work.
Perhaps there are cost-savings options that may be asked of a contractor.

Perhaps there’s a change in the project that opens up opportunities to revisit early design decisions.

But essentially, after contract award, there’s not a whole lot of leverage against complying with a bad set of specifications.

How do we address bad sets of bid documents in our industry?

If it’s life threatening and/or egregious, perhaps we could turn people into the governing boards. But how often is that done? How useful is it to permanently burn a bridge for reporting someone that may not even have any consequence?

The answer from those I speak with is almost never.

Consultants who don’t care about fire protection continue to issue plans and specifications, mostly the same as they always have, with little concern or incentive to change.

OUR INITIATIVE
Part of creating the community here is recognizing that uplifting everyone makes our industry better.

More knowledgeable contractors mean better detailed design and installations.

More knowledgeable plan review and inspectors means better policing and better final results across the board.

More knowledgeable consultants means that projects flow smoother, owners get what they need, and projects are more timely and on-budget.

Part of our responsibility here is to uplift the industry by sharing best practices and making helpful information & tools available that help us all do work better.

We have the educational piece (MeyerFire University), we have shorthand tools and cheatsheets. I write posts here. I have ideas in the works on helping improve access to basic, quality sets of specifications.

But what about now - as in today?

What is the best possible way to actually address a bad set of specifications that will get in the way of a smooth project?
 
PRE-BID RFIs
In my opinion, the most underutilized and best way to help foster a smooth project is challenging the scope before bid with a pre-bid RFI.

Pre-Bid RFIs (Request for Information) is a documented way to ask questions about the scope of a project before it is bid.
These can give an opportunity for a consultant to check their work, check their assumptions, give an opportunity to make a change if necessary, or give a chance to clarify an aspect of the scope.

Consultants can choose to play ball – help clarify the job on what should and shouldn’t be included. They can make changes if necessary, and allow bidders to bid apples-to-apples.

Contractors can also choose not to play – perhaps double down on the (incorrect) mantra of “this is the contractor’s responsibility to determine”, or something similar.

In either case, whether answered or not, Pre-Bid RFIs give the bidders either the information they seek or have greater permission (leverage?) to do as they see fit regarding the scope of the project.
 
SO MORE WORK FOR ME, JOE?
Crafting a good pre-bid RFI historically isn’t the easiest thing, though.

First – the writer has to digest enough of the project to write something coherent and competent – meaning they need to spend time looking through everything.

Second – pre-bid RFIs can sometimes have the presumption that a contractor is causing issues before they’re even on the job. This all comes down to the tone, silly as it might sound. If the pre-bid RFI is accusatory, that’s one thing. But if it’s written to help streamline a smooth project for everyone – then that’s a win for everyone.

Third – and perhaps the reason that pre-bid RFIs don’t happen as often as they should, is simply time. Bid days are time crunches. There’s a lot on the line. Going out of your way to clarify a project when you’re already on a time crunch can be tough.

This is the piece I’d like to help solve, and I think we can with some of your input.
 
THE CONCEPT
What if we had an automated tool that read a set of specifications and generated a helpful, appropriate, Pre-Bid RFI for your project?

While you’re reviewing the specifications and putting together your estimate, you do a 3-step copy and paste into ChatGPT (or something similar) that checks a whole host of specification issues and writes a Pre-Bid RFI for you?

You could have the time savings (huge), but also have AI do the work for checking for the 30 or 50 or 80 things that have been issues in the past – all stemming from specifications.

How convenient would that be?
 
If we could take the onus off of reporting bad players to state boards and instead focused on finding clean, appropriate, and easy ways to help make a project smoother for everyone – without adding any time burden – well that would be nothing short of awesome.
 
What I want to do from here is write a prompt and a step-by-step that I can share back with you all, that incorporates your list of grievances.

Essentially – everyone then has access to an easy way to gut-check specifications and get a custom-written Pre-Bid RFI out of it.

I need your input though to make it as useful for you as possible:
 
WHAT DO YOU NEED FROM ME JOE?
What I would love your input on is your answer to the following:

What have you seen in a specification that was clearly wrong which negatively impacted your project?

What have you found in a specification that makes bidding difficult, isn’t code compliant, or hurts the project?

I’m looking to create a list of checks that AI can do, for you, when it only has access to a project’s specification.

Comment below and let me know your thoughts – and in the next few weeks I’ll test and share a prompt and provide instructions back with you on how to use it. ​

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

​When you conduct a hydrant flow test, how precise is your resulting measurement?
 
Let’s say a flow test summary shows 82 psi static, 54 psi residual at 956 gpm.
 
Is it really 956 gpm? 

Well, no, of course – but 956 is the best resulting estimate of the flow test with the information and measurements we have at hand. It’s where the dial best predicts.
 
But how precise is that measurement, really?
 
Are we certain that it’s 956 gpm and not 957 gpm, or 960 gpm, or 1,000 gpm?
 
Now of course, a hydrant flow test is a point-in-time measurement. It’s not representative of daily fluctuation or seasonal fluctuation.
 
Let’s save that discussion for another time. What I’m really interested in is when we take a flow test or run a pump test, how accurate are our results, really?
 
SIGNIFICANT DIGITS
The concept of significant digits is one simple way avoid suggesting a higher level of precision than a measurement justifies.
 
In other words, if our flow test results said 956.21 gpm, we’re suggesting, based on the decimal placement that we actually know that the value is not 956.4 gpm; it’s instead between 956.2 and 956.3. That’s a level of precision that is suggested by significant digits.
 
Technically, if we had a pitot gauge reading of 9 psi during a flow test, then we would have one significant digit.
 
Using one significant digit is very problematic in flow test results.

​If you don’t think that’s a high-stakes proposition, then I’d invite you to wrap up final acceptance testing on a federal project with every stakeholder present and watching. It can be high stakes.
 
Perhaps the more appropriate way to understand precision is by doing error propagation on this conversion.
 
Error propagation is a sore point for me, as I pretty much failed every physics lab in college that required it. Time to shed those demons.
 
If you’re not into math, skip ahead to the summary to see where I ended up.
 
I want to show my work here as I haven’t seen this done and I’m very much for transparency and getting feedback, especially when I venture a little beyond my own fenceposts.
 
ERROR PROPAGATION FOR FLOW TEST CONVERSION
Error propagation is a fancy way to describe the reliability of the resulting calculation.
 
How precise is the result?
 
That’s what we want to know – and knowing so can help us make more informed decisions in our assessments. 

A formula with multiple variables, where each have their own uncertainty, the overall uncertainty depends upon how each variable affects the final result.
 
In other words – if I’m not exactly sure about the numbers I’m putting in, how unsure should I be about the answer I get out?
 
IMPACT OF DIAMETER VS. PITOT PRESSURE
In this equation, a percentage error in measurement of a diameter could have an outsized effect on the resulting flow since diameter is squared.
 
To run an error propagation on a formula involving variables which are multiplied together, we square the relative uncertainty (change in a measurement divided by the measurement), square them, add them together, and square out the result. 

​EXAMPLE: 60 PSI GAUGE
So, let’s say we ran a flow test where we were certain in the Coefficient of Discharge (0.90), we measured and were confident in the diameter of 2.5 inches (within a 1/16th of an inch), and took a pitot reading of two side outlets each at 8 psi using a 60 psi gauge with 1% accuracy.
​
Practically speaking, that’s a very reasonable amount of tolerance of a normal hydrant flow test or fire pump test.
​
With those results, we would calculate a total flow estimate of about 950 gpm. 

​How precise is that flow?

(Error in flow test reading measuring opening within 1/16” and pitot with 60 psi gauge)
​

So, with a variation of + 59 gpm, our resulting flow estimate would be 950 gpm + 59 gpm, or a resulting range of between 890 gpm and 1010 gpm.  
 
That’s a pretty wide variation – and it’s certainly a lot wider than I would have expected considering we’re using a 60 psi gauge with 1% accuracy.
 
EXAMPLE: 100 PSI GAUGE
What would happen if we used a 100 psi gauge with 1% accuracy?

(Error in flow test reading measuring opening within 1/16” and pitot with 100 psi gauge)
​

​EXAMPLE: 300 PSI GAUGE
Taken to an extreme – what if we used a 300 psi gauge to measure pitot? A bad idea for sure (it’s nearly impossible to read sensitive low amounts, and likely in the least-accurate portion of the gauge. But just for kicks:

​EXAMPLE: 60 PSI GAUGE WITH IMPRECISE DIAMETER
Now, what if we were less confident in the actual inside diameter of the hydrant side outlet? What if we thought it was 2.5”, but only within an 1/8th of an inch? With our 60 psi gauge:

(Error in flow test reading measuring opening within 1/8” and pitot with 60 psi gauge)
​

Yikes! Did you notice that?
 
Even with a 60 psi gauge, if we only know the inside diameter within an 1/8th of an inch, it’s worse than using a 100 psi gauge.
 
Knowing the precise inside diameter is important as it has a huge effect on the level of precision.
 
HOW DO WE IMPROVE PRECISION?
Based on the inputs – there are a few key ways to improve the precision of flow test readings when we use pitot gauges to estimate the amount of flow.

I’m interested in writing more on this in the coming weeks, but there are a number of ways in which we can improve the precision of our flow testing and have more confidence in our results.
 
#1 MEASURE THE OPENING SIZE
First – and probably the most important based on our calculation – is to know the exact diameter of the orifice opening.
If we are flowing out the side of an outlet, we actually need to measure, with precision, the inside diameter of that opening. As I’ve been told, not all inside diameters are equal. They depend on the exact make and model of a hydrant.

I’ve made this mistake before and assumed all 2.5” side outlets are the same inside diameter.

To improve precision, take a careful measurement of the exact inside diameter of the opening down to the 1/16th of an inch.

Alternatively, using a factory-created attachment with a factory-milled opening will help define and make that variation go away.

A known diameter with a very tight factory tolerance helps us reduce or eliminate this concern altogether.

#2 USE SMALLER RANGE GAUGES
In general, we want to use the smallest range for the gauge possible.

Using a 300 psi gauge to measure anything within 0-30 psi is problematic. Not only is that a less-accurate range for a gauge (near the ends), it’s extremely difficult to read. The tickmarks just become too small to read well.

Instead, we want to use the lowest gauge range that’s possible for the test.

If we’re expecting results below 100 psi, can we use a 100 psi gauge instead of 200 or 300?

If we’re measuring pitot and expecting values under 60, can we use a 60 psi gauge?

Even a 30 psi gauge?
​
The bigger the tickmarks and the smaller the range, the better we’re going to be able to see and read the results.

#3 LARGER-DIAMETER GAUGES
This goes against my “travel with small things” concept, but larger-diameter gauge faces are so much easier to read in the field.

They cost more. They’re bigger. But man are they easier to pull values from.

Again – on an important fire pump closeout with many people all watching – having nice clear results to prove the system works as it should helps.
 
#4 USE CALIBRATED GAUGES
For fire pump testing, NFPA 20 requires that all gauges undergo annual calibration testing and be accurate within 1 percent. (NFPA 20-2022 Section 14.2.6.1.2)

For fire hydrant flow tests, that same mandate doesn’t necessarily apply. NFPA 291 is a recommended practice, and requires calibration within 12 months, but is not necessarily enforceable in the same way that NFPA 20 is.

Now, if you’re on a federal project and NFPA 291’s “shoulds” become “shalls”, then there are enforceable teeth.

But for private practice work, many flow tests are simply run with whatever gauge is on the truck that day.

Using a calibrated gauge will obviously hone in for more precise measurement.
 
#5 USE STREAM-STRAIGHTENERS
NFPA 291 now specifically states a preference for playpipes or stream straighteners to improve the accuracy of readings.

Not only do these address the precise opening sizes we talked about earlier, but they hold the pitot measurements in a fixed-in-place mounting position.

This also means we should be measuring at exactly the right center-of-stream location.

This is explicitly listed now in NFPA 291 (2022) Section 4.6.2.
 
SUMMARY
Doing a little error propagation highlights a few things about the measurement process in a calculated way.

We can look at the accuracy of our input measurements an in turn, get a level of confidence about the resulting range of flow from those measurements.

The more precise we are able to measure, the more confidence we have in the result – which is both an obvious ‘gut-feeling’ but can also be mathematically proven.
 
YOUR TAKE
I’m interested in your take.

What are your tips for more accurate readings?

What stories do you have about fire pump acceptance testing or hydrant flow tests in this regard?
 
NEXT STEPS
I’d like to venture down this rabbit hole just a little further.

My next thought is to apply the error propagation concept into a quick calculator tool where you could see your error range yourself – and experiment with different situations.

You might just find an error range based on your normal test equipment that could present your test results in a more appropriate and transparent way.

That's TBD (to be developed).
 
Thanks for reading – and, as always, for fighting the good fight. Have a great rest of your week.
​
- Joe

 
#1 SHOW THE MEANS OF FORWARD FLOW (ADDED IN 2019)
A means of conducting a forward-flow test has long been required, but historically overlooked or was possibly achievable by flowing out of a fire department connection or main drain (for very low hazards).
 
We talked about the big change for a fixed means of forward flow that was introduced in 2019 and clarified in 2022.
 
How does this affect shop drawings?
 
Well, we now need to locate and identify the means of forward flow on the plans [NFPA 13-2019 Section 27.1.3(25) and 2022 Section 28.1.3(18)].