A few weeks ago I received a call from a sprinkler contractor who needed to provide a water supply graph for a flow test he conducted.
I had a canned sheet I had developed for my own flow tests, but it was a basic graph that showed a curve and didn't match the traditional N^1.85 hydraulic graphs common for water supply curves. Since then I've tinkered and come up with an accurate chart that takes flow test input values, calculates total flow and draws the curve along the N^1.85 chart.
The N^1.85 chart is particularly useful for fire suppression systems because the Hazen-Williams formula is based on the relationship that pressure relates to flow to the 1.85th power.
Take a look at the N1.85 Water Supply Curve tool here and let me know what you think in the comment section below.
When the x-axis, or the hydraulic flow is then scaled to the 1.85th power, hydraulic curves become straight lines which becomes easier to graph and compare. Prior to everyone carrying a computer in their pocket, these graphs were likely much easier to use for summaries and comparisons.
The water supply information is what is provided as part of a two-hydrant flow test. The design input information would be the system demand side and can be used for quick comparisons.
Personally, I only use this setup for flow test reports and water supply comparisons. Fire sprinkler hydraulic calculation software takes care of the graphs and outputs I need after I've completed the hydraulic calculations.
On a side note, I've had several people ask about getting access to all of the tools I've created to use on their own computer with the ability to produce printable output for record keeping. Thanks again to those who asked - that concept is in the works and I'm hoping to bring about some version of all-inclusive software in the next couple months.
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4/11/2018 09:06:36 am
I am trying to come up with a logarithmic graph form that we can plug in hydrant flow and it plots the curve / with a google map location for the hydrants / forms for fire hydrant insp. (5 year)
4/11/2018 12:02:30 pm
I keep getting failed to download chart. Is that just me or are others getting that as well?
4/11/2018 04:04:46 pm
Hi John, yes this is not yet available for download. I'll post back here when it is.
4/21/2018 02:57:03 pm
Deseo recibí r información
4/11/2018 12:35:37 pm
Thanks for putting this out! I just wanted to confirm that this is a web based tool only (like Ping Fire). My group has been looking to create an excel version for a while but has been running into issues with the N1.85 semi-log scaling. Do you have an excel version available?
4/11/2018 04:01:47 pm
Correct, yes this tool is only currently available online similar to Ping Fire.
4/11/2018 01:42:43 pm
Will this be available for download?
4/11/2018 04:03:31 pm
It will be a part of a software package with every tool I've created to date, but I don't have it ready quite yet. Should be posted in the next couple months.
4/11/2018 04:05:25 pm
Great tool! We've been working on a KCMO hydrant map with hydrant flow tests -- since the city will no longer give the information out. This form can replace my hand drawn flow test graphs using scanned N1.85 graph paper. Thanks!
4/11/2018 04:23:44 pm
The example showed up.. I have a free excel spreadsheet in my group on facebook - non-union fire sprinkler group. Feel free to join.
4/14/2018 05:58:59 pm
why are flow tests on log graph but fire pump data sheets on regular graph? Since most water flows are from pumps, would they look the same if plotted differently?
5/11/2018 09:56:04 am
If I am not mistaken, pump tests not plotted on log graph are actually curves and when plotted on log graph are straight lines like flow tests. I have seen flow test data and pump test data plotted on the same log graph to visually verify boost pressures.
4/23/2018 04:22:33 pm
when you have some calc program for download i'm interested to get one, on the other hand, I use before a software for NFPA 25 pump flow test... very usefull and easy, but unfourtunally does not run on windows 10, jut on XP. Did you Know some software to do that calcs and track the history maintenance.
4/24/2018 06:20:09 pm
Great tool! Is it possible to change the SI to metric? I'm from that part of the world.
5/10/2018 05:21:01 pm
Looks good. Can the units be modified to metric?
5/11/2018 06:29:47 am
Yes! The metric version is now available here: https://www.meyerfire.com/blog/fire-suppression-n185-supply-graph-now-in-si
5/17/2018 01:25:14 pm
What have all of you been using
7/5/2018 12:21:19 pm
Can you explain in your blog or to me how to adjust for Hydraulic Low gradient. There is nothing on the Web. No one seems to know, and I think my adjustments are too much?
Edriane Leonard Gabriel
12/20/2018 10:08:57 pm
1/5/2019 06:20:10 am
JUSTIN D STIRLING
1/5/2019 10:32:46 pm
I also have developed my own sheet with a basic graph that shows a curve. Can you provide any guidance on how to adjust the x-axis in Excel to make the N^1.85 chart? Thanks in advance!
1/3/2020 06:51:52 pm
I'm looking for a tutorial explaining how to evaluate hydrant flow tests and manipulate various flow senarios.
8/3/2020 07:55:59 am
never got my access code for the trial
8/3/2020 08:01:18 am
Comments are closed.
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Joe Meyer, PE, is a Fire Protection Engineer out of St. Louis, Missouri who writes & develops resources for Fire Protection Professionals. See bio here: About