Fire Water Piping Pressure

A full explanation of this depends on the "pump curve" of the particular fire pump, which shows how the flow and pressure vary with each other. Opening up two hydrants approximately (but not quite) would double the flow from the pump, and drop the pressure to about 71%. That is a big oversimplification; details vary with the specific pump curve, and where the two flows/pressures are located along the curve.

Googling "pump curve" will probably give some better explanations.

For thumbnail calculations, I sometimes use hp ≈ gpm x psi ÷ 1200. (As I recall, the theoretical value is ~1752 rather than 1200, but using 1200 equates to a pump efficiency of 0.685, which is conservative for large pumps.) By using conversion factors, one can derive similar rules of thumb for other units.

I think I need non-technical explanation.

Determine how many hydrants you need to operate at one time. Your fire pump should be rated at 175 psi. Base your calculation on 150 psi as a safety factor. Multiply hydrants by gallons per minute per hydrant (determined by hydrant size, refer to hydrant spec. sheet). This gives you flow of system in GPM. Size your pump according to this requirement. There are other factors in play as well like coefficient of friction and hence pressure drop in piping to hydrants, but this will get you started.

Ok, I will ask in different way.

If I have one waterspout with valve. The water source inside the pipe is constant. So, if I want to have a big and full flow, I will open the valve all the way down. But if I want to have a smaller and further water jet, I will partially open this valve. But now, the water jet will become stronger and I could be wet with it.

The same question for for fire water here. Could we keep the balance between one hydrant and five hydrants?

I live in Toronto, and when there is a large fire = more hoses and trucks, they can boost the line pressure to supply more water. I do not know what the absolute max is.

If you can add more pump to the system, maybe. Or your pump is able to detect drop in water pressure when valve is open and increase flow.

Simply put. To get full flow in 5 outlet you'll need 5 pump. Or a pump with 5 times flowrate of the one you use now.

You cannot keep all 5 pump running all the time. You system pressure will be too high.

Now the question is: is it a requirement of the system to maintain same flow rate in all 5 hydrants?

Good day to you. I have just started to read the threads to your inquiry. I am a firefighter, with a coastal community in Oregon, USA. What I am interested in is the following items as these would help me to understand your dilemma a little better. What is the area that you are looking to protect, please state by whatever you use to measure such as liters, square footage, etc. Now, what is the main thing that is needing protection, such as manufacturing of some sort, residential area such as a care center for ill/injured people, rubber manufacturing, fuel depot...this will influence the design requirements. Is there a water reservoir that is being utilized for you to pump from, and is it a man-made or natural reservoir system? Have you any idea of the gallons or liters it stores before a flow is required? Have you a stable intake pipeline of one size from the reservoir to your point of need, or is it a combination of various sizes? Are you the only one that will be placing a demand on that reservoir or is it subject to other's needs as well? I think I understand your terminology, but I want to be sure that I do. On the description of the waterspout, I believe this is what we would refer to as a nozzle. If this is correct, is this a straight bore, or is it adjustable by mechanical or automatic means? This would control the output in terms of gallons or liters/minute. It is common to have the flow become stronger as the orifice of the nozzle is made smaller, regardless of the pump or water source. Given that as a common problem there should be some training to enable the firefighter on the end of the nozzle, ( we call the business end, ), it is entirely controllable in the long run.

On the hydrant issue, the size of the mainline piping serving the layout can influence your firestream as well, let alone worrying about what size pump to install. How many hydrants will be served off of that particular mainline will greatly influence your system performance. In my city, the brains of the design staff had no clue about properly laying out an efficient firefighting system, so we have a closed loop with only on size pipe feeding 6 hydrants, no booster pump, and if we open one hydrant, and we need more pressure on another hydrant, and we hook in a fire engine to boost the pressure at that engines area, we basically screw our buddy by robbing him of water. We can actually cause a collapse if we were to really put the demand on the layout as plumbed. I anticipate this is something that you would like to avoid. We use other trucks we refer to as water tenders to haul more water to this site, which, by the way, is one of the largest shopping centers in our area. Another issue altogether, but an option that you might want to put in the back of your mind.

If you would please provide those answers, I believe we may better serve your inquiry. I am thinking those answers will give a baseline for more accurate thinking through your inquiry as well.

Thank you. DLC

Dear Fire Fighter, May I request you to also comment on following thread posted by me:

"Fire Alarm/Suppression System For Underground Ore Conveyors"

Pritam: Good day to you. I will have to dig into the CR4 archieves to view your posting as it isn't poppin up on this thread. I anticipate an interesting post based on the title alone of your comment. Thank you, and I will get back to you after I review it. DLC

For the design of a firewater pipeline system on petrochemical and industrial plants, the total required minimum capacity of the net is to serve 3 adjacent hydrants (2x3" outlets ea) at the same time which totals on 360 m3/h (1583 GPM) with a minimum outlet pressure of 3 Barg (43.5 psi) on the farthest end. The configuration of the net is a ring circuit.
The pressure rating of the piping is 10 or 16 Barg ( 145 or 232 ).
If this pipeline is also used to tap small quantities of water a jockey pump is installated beside the big firewater (diesel powered) pump.

Fully agree with Galala. GA.

All outlets of fire hydrants pressure should be same as per the design or to match with the local fire code standards. As explained by Mr. Abdel Halim Fire stations need to have diesel pump in addition to normal pump for emergency purpose.