Hand Method for Calculating Friction Loss for Firefighters 

Thank you!

clark barton IV Thank you very much. We are looking at producing more video series and hope to start them soon. We also have a nozzle series which goes fairly well with pump operations if you haven't seen it.

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Ben Turner Thanks, I appreciate it!

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Not quite. The 100-200 is just the GPM from whatever nozzle you are using. Once you know what your GPM is, you then use the corresponding muliplier and multiply by “12”. Hope that helps. That will give you the FL per 100’.

I learned this way as well

Other methods, like the drop 10 method, support started with 3.

That is a very good question and I completely understand where you are seeing these. I am not sure why some texts have decided to change the 12 to a 9 on the hand method but my math puts the "9"" way under what the pressure should be. Ultimately, we have to get out a flow each of our own systems to see what the discrepancies are but here is an example: The actual FL for 200 GPM through 100' of 1.75" is 62 psi. Using the "12" hand method will get you 60 psi (pretty freakin close). Using the "9" hand method will get you 45 psi... This is pretty drastically lower than what it should be. Increase that to a very common 200' attack line using the "9" and you are 35 psi beneath the required nozzle pressure. We actually use a text book at our academy that shows both the "12" and "9" in different printings of the same text. I was told this was a typo but also saw it in a brand new text I was reviewing for a publisher. I'm not sure if I am helping at all but this is what I know... haha

Thanks Matt. I was just reviewing and noticed the older book I had showed 9, but I also did the formula and noted that 12 is much closer all around to the formula. Thanks for the reply! You're definitely helping, keep up the good work!

Matt Hinkle I think the MFGS have started to change with the new High Combat technology that is giving more water w/ less friction loss. While I understand some people saying figure this out in the station and I agree. This type of "rough math" is helpful when you have to extend the hose load 100' on the fly. A fairly common occurrence when using a courtyard lay. In our 1st due. we have big houses on long driveways, with no hydrants (Tankers and drop tanks) At almost any instant your pre-connects get CHANGED to accommodate a need. These shortcuts help a lot.

Yea, I have read other text books that show using the number 9 in the palm instead of the number 12. That will drop your friction loss down to something more like the High Combat or the Ponn Conquest. If you use a lower coefficient hose I would go with "9" if not I would stick with "12". Best thing to do is flow test your current setup to get a good baseline that way you know where to go from there.

@@Boxalarmtraining The old method is a 9 multiplier, the new method is 12.

Dale Lewis did you ever figure out the drop 10 method? It’s good to know. It works for 2.5” hose. For example: an 1 1/8 smooth bore flows 265 gpms. So you would first drop the 5. Then subtract 10 from 26 which leaves 16. That’s it. Your fl is 16 psi per 100’ of 2.5” hose.

Steve Hutchinson use the same method, should get you close to the adequate gpm required.

This hand method uses coefficients provided from a text book when this video was produced. The coefficients vary greatly depending on the hose construction and actual internal diameter. There is a significant different in coefficients between a 1.75” and a 1.88” internal diameter but both of those hoses are called an 1 3/4”. The only way to actual determine your PDP is to test your own hose lines and attack packages. Even a 50’ hose line is not actually 50’. If you open the box on several sections of new hose that are labeled 50’ they will almost never actually be the same length. I’ve seen hoses differ by more than 5’ but both called 50’.

That's perfectly fine for your operations and I prefer charts exactly like you are saying. I made this video to explain this method because many get confused and have to learn it for tests or promotional exams. Some actually like this method but my experiences generally lead to finding the method(s) you prefer and sticking to them. If you like pre-planning and making charts then I couldn't agree more. Glad to hear you all are taking the time to do that.