# Thread: Supplying sprinkler systems

1. ## Supplying sprinkler systems

Hello again, ok here is the question of the day at the station, with the up coming drivers test, question's are flying like kamakzi pilots.

when supplying fdc's for the sprinklered building, do you add elevation loss, and 25psi for the fdc??

Thanks for you time.
Jgreen PTB EGH

2. 150 psi. You cannot add anything or calculate any frictionlosses or elevation losses. This is a huge common mistake for most departments. Unless you're a fire protection engineer witht he right info anything but discharge pressure is nearly impossible to predict. Yes, alot of people will say, "BS" so I offer a few questions for those who think they can pump 150 at teh FDC or anywhere but the pump:

1. What's the outlet(nozzle) size?
2. Directly related to #1: What's the flow to be supplied in GPM?
3. What is the friction loss in the system?
4. If you think you can calculate friction loss in pipe (you can) how do you figure looped lines or primary/secondary feeds?
5. How many heads are fused? What is the flow of each head?

You see, there are too many variables to figure out. But if you supply 150 psi at the pump, the system has or should have been designed and built to handle this pressure. It should be all you need unless the place is burning down in good shape. If the heads are flowing as much as 30 gpm, how many can trip before your 1000 gpm pumper flowing 150 psi through a 4" line or 2 2.5" lines? Given that your supply engine can flow it capacity at draft at 150 psi if you discharge 150 into 200ft. of 4" you ought ot be pretty well set for a few heads!

This question comes up 1-2 times a year in our dept. Its fun to watch people try and answer the correct calculations.

3. I should add that the pump operator should try and maintain the 150 psi the whole time and may want to tell the IC or sector officer if there is ahuige drop in psi as this may indicate a break in the sprinkler system or a large number of heads tripping.

4. Thanks for the help.... I knew it would be only a matter of time for an answer. Good stuff.

5. 150's the way I learned it as well. The only pressue I've been told to add is a little if there's a long lay to the inlet of the system (which shouldn't be an issue in most cases). The along with what RFDACM said, if you have trouble maintiaining 150 or you keep having to add pressure, you either have a more heads going off or the possibility of one of the pipes busted.

6. This question comes up at least once a month in my department. I agree with 150 psi.

7. Remember to SLOWLY build up your discharge pressure to 150 PSI.

8. Not to hijack the thread, but standpipe and sprinkler systems are great drills for ECCs. At work, we have a couple buildings where the ECC drops us off, and has to drive a block away to hookup to the standpipe or sprinkler system. Knowing your pressures and things of that nature are a great way to get inexperienced ECCs some work.

9. Originally Posted by RFDACM
150 psi. You cannot add anything or calculate any frictionlosses or elevation losses. This is a huge common mistake for most departments. Unless you're a fire protection engineer witht he right info anything but discharge pressure is nearly impossible to predict. Yes, alot of people will say, "BS" so I offer a few questions for those who think they can pump 150 at teh FDC or anywhere but the pump:

1. What's the outlet(nozzle) size?
2. Directly related to #1: What's the flow to be supplied in GPM?
3. What is the friction loss in the system?
4. If you think you can calculate friction loss in pipe (you can) how do you figure looped lines or primary/secondary feeds?
5. How many heads are fused? What is the flow of each head?

You see, there are too many variables to figure out. But if you supply 150 psi at the pump, the system has or should have been designed and built to handle this pressure. It should be all you need unless the place is burning down in good shape. If the heads are flowing as much as 30 gpm, how many can trip before your 1000 gpm pumper flowing 150 psi through a 4" line or 2 2.5" lines? Given that your supply engine can flow it capacity at draft at 150 psi if you discharge 150 into 200ft. of 4" you ought ot be pretty well set for a few heads!

This question comes up 1-2 times a year in our dept. Its fun to watch people try and answer the correct calculations.

150 p.s.i. from the pump max. Don't try to second guess anything under 4 stories. Your elevation loss is going to be .433 p.s.i. per linear foot of elevation. You might be supplying a 6" or a 4" standpipe. Your friction loss is significantly different from 4" to 6". You can count on approximately 12'-0" from finished floor to finished floor. Also, each sprinkler head, depending on the occupancy, has a minimum operation pressure. Most light hazard occupancies utilize heads that have a 7 p.s.i. operating pressure. If you're talking about storage facilities and warehouses, all bets are off...especially where plastics are concerned. Are your sprinkler heads a K factor of 5.6? Are they 11.2 K factor heads? What if they are 25's? When the most remote area of the system is calculated, the flowing area is calculated based on a density. That might be 900 s.f., or 1500 s.f. It could be 2500 square feet. That's the condition where no fewer than 5 heads are flowing at once within the design area. I have designed systems that were flowing 19 heads within a 1500 square foot area. That's a pretty high demand on a city supplied system.

To answer your question...I'm sure you are seeing just how involved it would be for you to hydraulically spec your pump pressure. I would, however, consider what floor my fire was on, and adjust for my elevation. Just remember that if you are adjusting for the system flowing on the 8th floor, you are still putting pressure on the system on the first floor. Did I mention that the system components were only rated for 175 p.s.i.? Confused yet?

10. We also use 150 as our "Rule of Thumb", but add standard calc's for long supply lays over 100'.

We also have combined standpipe/sprinkler pipes, so the interior team is supposed to report to the operator with the standpipe residual at the connection point (gauges are usually built-in in our community). He will then adjust to ensure they have adequate pressure.

Good point about the max pressure for the lower floors, as too much pressure could cause a catastrophic failure there, and divert most or all of the upper floors (and hose teams) water supply.

11. We rarely have long lays to the FDC. The codes here call for them to be within a short distance of the hydrant and I beileve many places are like that.

12. Could someone explain how they calculate any additional losses added in? I fail to see how you can add friction lss without knowing the flow. The 150 psi is a sort of shot in the dark number. Its less than the max system pis of 175 but enough that it can handle whatever your pump can deliver (draft source not positive source).

If you hook up and there is no open heads you will quickly equalize the system and have 150 psi with nearly no RPMs. If you have single head go you may not even see the drop in pressure. What if you had only 4 heads operating for about 100 gpm? Why, if you knew, would you pump 150 psi? Trying to flow the capacity of your pump through 4 heads is ridiculous. maintaining 150 psi is just a guarantee that you can deliver all you can deliver if it becomes necessary.

Another ex: if one head trips on the fifth floor and your PDP of 150 drops to 147psi why would you add in friction loss? Can't you pumper supply 13-30 gpm to the fifth floor at 150?

There is a reason that the 150 is measured at the pump and maintained at just that. Without prior knowledge of the system design and the number of fused heads and their points in the system, you cannot figure out friction loss or any other losses.

To sum up the good points made above:
Connect the system with 1 LDH or 2-2.5-3" lines as short as possible.
Slowly bring the PDP to 150 psi
Maintain the 150psi and notify the IC if there is asudden drop or large drop.

This can also be a great indicator of how well your not doing, if you have to keep increasing RPM to maintain 150, your losing!

13. RFD,

Your analysis is probably fine for a separate FDC supplying sprinklers only, but if you are working to maintain the sprinkler flow plus a 200gpm handline on a combination system, you may very well need to compensate.

Most of our larger buildings are 5-7 stories with combination Standpipe Conn/Sprinkler systems. In the most extreme example, weather, idiot parking jobs (blocking a fire lane, etc.), and other factors could result in 200 foot FDC lays, with 7 stories of elevation, plus your sprinkler flow, and up to 200gpm demand on a small handline. You will need to be prepared to compensate in that scenario to maintain the reccomended 100psi @ 200gpm to the nozzle.

Also, as mentioned, large industrial applications can flow significantly more than the 30gpm listed and often at higher pressures.

14. Originally Posted by mcaldwell
RFD,

Your analysis is probably fine for a separate FDC supplying sprinklers only, but if you are working to maintain the sprinkler flow plus a 200gpm handline on a combination system, you may very well need to compensate.

Also, as mentioned, large industrial applications can flow significantly more than the 30gpm listed and often at higher pressures.
Agreed on both counts! I'm glad you pointed that out.

15. Thank you to all, for the input. That is what I learned in Pumps and Hydraulics also 150psi increasing in 25psi increments not to exceed 200psi. But the question was brought up, and it started to stir up thoughts and conversation.

16. Originally Posted by mcaldwell
RFD,

Your analysis is probably fine for a separate FDC supplying sprinklers only, but if you are working to maintain the sprinkler flow plus a 200gpm handline on a combination system, you may very well need to compensate.

Most of our larger buildings are 5-7 stories with combination Standpipe Conn/Sprinkler systems. In the most extreme example, weather, idiot parking jobs (blocking a fire lane, etc.), and other factors could result in 200 foot FDC lays, with 7 stories of elevation, plus your sprinkler flow, and up to 200gpm demand on a small handline. You will need to be prepared to compensate in that scenario to maintain the reccomended 100psi @ 200gpm to the nozzle.

Most high rise applications are based on a combination system utilizing a wet standpipe with 2.5" hose valves. When we design a system, we count on the pumpers to be able to provide 1000 gpm with a max pressure of 250. Naturally, we don't anticipate a full 250. The added ability is reserved for hand lines and a large area flowing on the system. Besides that, there are supposed to be PRV's placed in line on the hose systems to keep us from rocketing through a wall when we open up the nozzle.

Also, as mentioned, large industrial applications can flow significantly more than the 30gpm listed and often at higher pressures.
It's fairly easy to anticipate higher demands in industrial applications; however, large retail outlets such as Best Buy, and other stores that have a lot of plastic storage over 15'-0" in height will have a high demand, as well. I just finished a Best Buy in Lake Charles, LA that had a density of .45 gpm/2500 s.f. for the stockroom. That's pretty much standard for their chain. The salesfloor was .24 gpm/2000 s.f.

Anytime you pull up on a Wal-Mart or a "warehouse superstore" you might find yourself wondering why you're having to increase your pressure so much, depending on how involved it is.

17. With the digital pump panels, it shouldn't be too hard to maintain pressure when it's operating in PSI mode. It's when you're trying to keep up in RPM mode, or with analog gauges that it would be a royal ***** pain. I know that we're trained in analog, though...so I'll take my technologically brainwashed butt to the rear of the class now! LOL

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