A Discussion on 4" LDH vs 5" LDH,

by Phil Lemire

Mar 22, 2008

My City is contemplating Going to 5" LDH. We currently use 4", and have water problems at significant fires. I am advocating the 5" purely from a hydraulic perspective. We currently have 2 -1500gpm triples, and 6- 1250's. The 4" has been OK. for the 1250's and our retired 1000gpm's,but now with 1500 pumps, I feel 5" LDH is needed to flow those volumes! Some disagree, and the biggest argument is the Weight of the 5" LDH hose? If you are currently using 5" LDH, please weigh in on this discussion.
Thanks
Phil Lemire,
P.S. I assume the Strotz couplings are different as well?
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  • up

    Chris Mc Loone

    All engines in my department except for one carry 5" hose. If we lay a line for a fire, it's rarely anything but 5". My company runs two engines, each carry 1100' of 5". We have drilled using several different elevations and several different length hose lays and have foudn 5" to acommodate the flows we need. That being said, the 5" would be useless if we didn't know where to find good water. I would start with your water supply. If your supply is inadequate, making the move to 5" at this point may not be worth it. For your longer lays, consider placing pumpers in line using some sort of valve like a Humat to help move the water. Doing so should help you not reach the 180 psi in your case, or 185 psi limit of 5" hose. The friction loss with 5" is definitely lower.

    Also don't forget to put your biggest pump at the hydrant.

    Chris Mc Loone

    Mar 23, 2008

  • up

    Darren Sluder

    My department has been using 5" for 12 years or so and have only used 5". However, according to the manufacturer training videos, 5" supplies considerable more than 4". I know this sounds silly but mathmatically, it works!
    Angus Brand hose had a really good video on choices of 5" versus 3"and 4" hose.
    You will need to change your truck and hydrant fittings as well as any adapters that are 4" storz. That alone is quite a cost however, the benefits out weigh the cost in my book. You might check out the angus web page to see if a video etc can assist in the friction loss analysis and fire flows.

    Mar 24, 2008

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    Don DeBias

    Phil.
    Are department has always used 5 inch since i joined so the weight is something i cant compare. as for volume its great i have pumped at fires with a 1000 feet of 5 inch on the ground my engine at the hydrant with a 5 and 3 inch on the hydrant to the engine and attack pumper feeding 2- 13/4 fogs and 2 1/2, engineer said he had 30 psi left on intake gauge. we run with 25 feet on front and side suction, 800 feet in rear bed. At training we ran supply engine at hydrant off that another engine and one quint, with quint flowing and 2 deck guns and numerous hand line we estamated 3000 gpm(based on tip size and pressure). one note we have good city pressure. all stortz. our dist is all the same we carry some adapters.

    Mar 26, 2008