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Low Pressure Fog: 50psi vs. 75psi

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  • Low Pressure Fog: 50psi vs. 75psi

    We're upgrading our nozzles, and half of our 1 3/4" lines are going to get 15/16ths smooth bores, while the other half are going to get 150 gpm low pressure fog tips. For current users of the LP fog, is there any preference between the 50psi stems vs. the 75 psi stems in the 150 gpm range?

    I realize that the 75psi is 25 psi higher, will have slightly more nozzle reaction, slightly more reach, and slightly less kinking.

    Current users?

  • #2
    Overhaul Tips

    Also, just to piggyback onto my last post:

    For department's using smoothbores (15/16ths, primarily): do you use the double stack with the 1/2" (50 gpm) overhaul tip option, or just the simple, single tip 15/16ths?


    • #3
      The Chief nozzles offer a break apart nozzle. 15/16 smooth bore and then the fog head screws on. You can get the fog tip set up for 200 GPM at 75 psi tip pressure. Here's an example 1 3/4 hose with 150 GPM nozzle: 150 foot line 100 psi tip. pump pressure is 148 for 150 GPM where as with the chief nozzle instead of 100 psi at the tip it's 75 but an increase from 32 per hundred feet to 50 psi per hundred equalling 150 feet 1 3/4 75psi and chief nozzle 75 psi totalling 150 pump pressure. Other nice thing is 200 GPM orfice is bigger so less nozzle reaction and 50 more GPM with a total increase of 2 psi overall. We tried the 50 psi nozzles and had way to many kinking issues with them.


      • #4
        We just use the single 15/16 tip.

        As for pressure options, I would tend to think it depends on how you are going to use it. Off the engine, or as a standpipe line. The 50psi tip would better take advantage of available pressure in an extra long lay, off one of those wonderful pressure reduced standpipe outlets, or off an ldh manifold.

        We still use 100 psi TFT's, so I don't have much practical experience to share with these. We did get an Elkhart Chief to play with a few years back, don't know which pressure option it was though. I do remember liking it better than the high pressure autos! I'm not in charge of purchasing, though...


        • #5
          Several years ago an FD I worked with received an FEMA grant for new nozzles and hose. We decided to make everything as easy as possible for a small volunteer FD with minimal fire work. We chose the 7/8" tip for the solid bore and Akron Assault low pressure at 150 gpm at 50 psi. All the 2.5" nozzles also use 50 psi as the nozzle pressure so the drivers only had to remember one nozzle pressure for any line. Both nozzles have about the same flow and based on the FF's experience and comfort level, they can pick either a solid bore or fog tip. We found an article about the FL used by FDNY on their 1.75" lines. We found the flows were closer to the 165 gpm rather than the 188 gpm (this is based on the article, not anything official) so we went with the 7/8" tip. My FD uses the 7/8" on the 1.75" and the 1 1/8" tip on our 2.5" lines. We have found they work just fine. Having all the NP's be the same really makes it easy for the engineers.


          • #6
            My volly FD has been using 200 gpm at 75 psi Elkhart Chiefs for about 10 years now. They are break aparts with a 1 1/4 inch slug tip. We use this set up on 2 inch hose. The pistol grip shut off with the slug is an Elkhart model B275GAT and the tip is an Elkhart model 4000-24.

            We underpump the 200 at 75 combo tip to around 55 psi to flow around 160 gpm to start and then go to 75 psi to flow 200 gpm if needed. We have had no issues with kinking.

            My career FD uses 150 gpm at 50 psi combos on our crosslay 1 3/4 lines, 250 gpm at 75 on our 2 1/2 crosslays, and 1 1/8 smoothbores on our high rise pack 1 3/4 inch lines. I have used the 150 at 50's yet they are brand new, the 250 at 75 handles fine and there have been no issues with them. With the 1 1/8 inch tip there is some kinking but the hose doesn't seem to be affected much by it and the flow is not reduced very much by folding the hose completely in half.

            My preference is the 75 psi tips for combos.
            Crazy, but that's how it goes
            Millions of people living as foes
            Maybe it's not too late
            To learn how to love, and forget how to hate


            • #7
              BlitzfireSolo, we use Akron Assault breakapart nozzles. Adjustable tip is a 75psi/175gpm. When the tip is removed, it's a 15/16" smoothbore slug.

              We used a flow meter and found the proper pump pressure for our hoses that gives us 170-180gpm, regardless of whether the tip is on the line or not. Makes it very easy for the pump operator as he pumps that 1 pressure and does not have to worry about what tip is on the line.

              We have 2 or 3 older nozzles still in use, but they will be replaced very soon with the same setup.

              Haven't had any kinking issues and haven't had any troubles moving the lines.
              "This thread is being closed as it is off-topic and not related to the fire industry." - Isn't that what the Off Duty forum was for?


              • #8
                Originally posted by BlitzfireSolo View Post
                We're upgrading our nozzles, and half of our 1 3/4" lines are going to get 15/16ths smooth bores, while the other half are going to get 150 gpm low pressure fog tips. For current users of the LP fog, is there any preference between the 50psi stems vs. the 75 psi stems in the 150 gpm range?

                I realize that the 75psi is 25 psi higher, will have slightly more nozzle reaction, slightly more reach, and slightly less kinking.

                Current users?
                Any thoughts, comments and ideas on the use or replacement of the Vinidcators you were running?


                • #9
                  I like the idea of having one nozzle pressure and one flow to remember. On the 1 3/4" lines, 175/50 fogs and 15/16" smoothbores work well. Same nozzle pressures and close enough flow ratings to pump the lines the same. On the 2 1/2" lines, 250/50 fogs and 1 1/8" smooth bore non-stacked smooth bores. Same concept as before; same nozzle pressures and the same flow.

                  This way, no matter what line you pull, you only have 2 engine pressures to remember. If you are using conventional hose like most departments do. you will have to pump it high enough to not have to worry about kinks. I am also a fan of the Elkhart Chief nozzles. I will never write an order for a nozzle with plastic peices ever again.
                  Career Firefighter
                  Volunteer Captain

                  -Professional in Either Role-

                  Originally posted by Rescue101
                  I don't mind fire rolling over my head. I just don't like it rolling UNDER my a**.


                  • #10
                    Thanks for the input thus far.

                    Overhaul Tips
                    On the overhaul tips, they do add to the cost of the 15/16ths tip, but it just seems like a good idea to have that extra option for...overhaul and such. But maybe it wouldn't really get used? Simply gate back or under-pump the 15/16ths once you get to the point of overhauling? However, having the 1/2" tip seems like it would be really good for "tunneling" through rubble and accessing other deep-seated hot spots when needed.

                    Fog Tips
                    The idea of a 150 or 175 gpm fog tip with the 15/16ths slug behind it is a good one, but our built-in slug tips on both the 150 gpm fog and the 15/16ths nozzles will be 1 1/8" orifice. With our gradual upgrade to Ponn Conquest 1 3/4" hose, this will give us the option to really knock the snot out of the fire if we find that we need it once inside (otherwise we'll have our 2"x2 1/2" line for 250-325gpm flows).

                    I'm leaning towards the 50psi 150gpm tip, on the idea that we should be able to slightly over-pump it (165ish GPM?) and have a common pump pressure with the 15/16ths smoothbore lines. I do really like the idea of having a single pump pressure for the same size & length lines, if possible.

                    GT - I agree with you on the plastic issue. That's one of the primary reasons we're buying all Elkhart for this project.

                    Adam, for the most part, we've only used the Vindicators as secondary nozzles. When it came time to evaluate our nozzle upgrade on Engines 1 and 2 (from crap TFT automatics), we did consider the Vindicator as an option. In the end, we ended up going choosing smoothbores due to:
                    - 180gpm pressure: Vindicator Heavy Attack is 250gpm at 50psi, while we wanted to flow 180gpm at 50 psi
                    - Stacked tips: Can't stack tips on a Vindicator, where we wanted both 250gpm @50psi AND 325gpm @50 psi on our 2"x2 1/2" lines.
                    - Simplicity: while Vindicators may only have one moving part to break, wear or maintain, smoothbores have none.
                    - Noise: While it certainly would not have been a deal breaker on the Vindicator, it didn't help it either.
                    - Size: Again not a deal breaker, but the SB's compact form is nice.
                    - Debris: While the Vindicator is pretty good with debris, still nothing beats smoothbore.
                    - Cost: Nothing's more cost-effective than a simple SB tip.
                    And so when all of the above was considered, it didn't seem advantageous to pay more to have something that didn't offer a tremendous advantage besides better foam production.

                    Thanks again for the continued input.

                    Edit: I'm also not going to lie about the role that culture plays with the Vindicators - it's a lot easier to sell the idea of LP fogs and smoothbores than the unorthodox Vindicator. Just FWIW.
                    Last edited by BlitzfireSolo; 12-09-2010, 03:56 PM.


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