Do I need a fire pump for this sprinkler system?

[m2e]

Hi I need some urgent help and would really appreciate any comments. I've tried to read NFPA 13, but couldn't find an answer yet.

I have a building with 3 major zones that needs sprinklers.
1. A single-story warehouse with about 14000 sq.ft.
2. Several mechanical and storage rooms
3. A two-story display center kind of building with about 3000 sq.ft total. They're all attached to each other.

The incoming water from the city is 90psi. The highest point for the building is about 32ft.

The warehouse should be Ordinary hazard Group 2, and the display center is light hazard.

Question:
1. Do I need a fire pump in the building to boost the water pressure?
2. How do you sub-divide the zones? Should each floor in the display center have a zone?


Thanks.

 

[pipesnpumps]

Is this a joke? All I can say, IF you are designing this,is walk away. You really need to come clean with your management, or your client, or whoever is depending on you to do this design and call in outside help who knows what they are doing.

What you are asking is like me signing a contract to design a rocket to go into outerspace and posting on a NASA message board, "help, I've got 3 days to figure out the correct hydrogen to liquid oxygen ratio to supply a rocketship I'm building".

Perhaps you have a more senior engineer in your organization. Perhaps you have a colleague from a professional society you could call and ask to help you understand the fundamentals, explaining your predicament, but whatever you do, please don't expect to be able to thumb through a fresh copy of NFPA 13 and answer these questions well enough to complete a design.

Sorry if this comes across as harsh, but situations like this make those who work within their areas of expertise look bad. Best case, the Sprinkler contractor's NICET will come behind you and clean up your mess, worst case the responsible PE gets sued for the errors and omissions..

 

[ChrisConley]

I'm trying to decide if you are looking for a rule of thumb that tells you if you need a fire pump in prelim design, or if you are doing the full design. I'm going to assume this is for preliminary design only.

My apologies to actual fire protection engineers, but often the project mechanical engineer (no fire protection engineer hired or available) is asked to do preliminary sprinkler design. This is particularly true in areas where the sprinkler design falls 'neatly' into NFPA 13 and (as pipesandpumps mentions) the Sprinkler contractor is expected to clean up the drawings. We don't always have the tools to do the full design, but are still expected to figure out if a fire pump is needed.

If you figure out the areas of the 'worst zones' and the required coverage (gpm/ft2) both are listed in NFPA 13, you can calculate a flow rate. Using this flow rate, the largest mains you can use and basic hydraulics you should be able to estimate if you have enough pressure (residual or static at 90psi btw?) at the street to get required pressure to your sprinkler head. Different heads, different pressure requirements, but for estimating 15 psi should get you started (keeping in mind that these are just preliminary calculations).

If you are close, a fire pump shouldn't be required, if you are very short then you will need a fire pump. I haven't seen many low rise, OH, buildings with 90psi available require a pump.

If you do decide you need a pump size the pump large, but allow the Sprinkler Contractor to downsize when they finish their hydraulic calculations.

 

[stookeyfpe]

M2E

Normally I'm the most sarcastic of the members in this forum so in their defense I agree with their responses because your asking a complicated question without a lot to go on.

For example, a 90 PSI static pressure tells me nothing. We need the residual pressure and flow from the hydrant to begin to conceptually understand if a pump is required.

I'm not understanding what a 2-story display center kind of building is. Is it retail display, does it have high-piled storage?

I'm going to completely speculate and tell you your warehouse is probably going to require the largest hydraulic demand. But what's storing and how is it stored?

Finally, is this in the US because if it isn't we have a few Canadian members and less from Europe or Asia.

Remember without any design schematics, it's hard for us to even speculate on what's required.

 

[skdesigner]

@ Chris Conley - "This is particularly true in areas where the sprinkler design falls 'neatly' into NFPA 13 and (as pipesandpumps mentions) the Sprinkler contractor is expected to clean up the drawings."

From a sprinkler designer, that's what I call job security in good old saskatoon, saskatchewan.

 

[NJ1]

If all you are looking is for a comment or opinion then I will have to say no, You do not need a fire pump in this application however if you are performing any scope outside your experience and background then you need to back off and let a PE or NICET Designer do this for you.

It seems you are using this forum to bail your ass out of this one.

90 psi static will leave you with approximately 70 psi at flow and 85 residual if such pressure is consistent. Then you have 14000 sq feet and 3000 sq feet plus several mechanical rooms.
Are you kidding me? I have seen buildings bigger than this without a pump.
Warehouse must maintain storage rules to a minimum to avoid racks sprinklers but then again I am sure you already know this.
Good Luck with your sprinkler 101 adventure

 

[FFP1]

Be very careful.......I have seen static pressures of 85-90 psi with residual pressures dropping as low as 30-40 psi while flowing 1,000-1,200 gpm in some rural areas. So many factors to consider. A person with a significant amount of experience MIGHT be able to estimate a residual pressure and flow IF the facility is fed by a gridded public system with >8 in. mains fed by a system of gravity tanks (along with confirmation that the underground mains are not affected by tuberculation of course); however, assumptions like these can be VERY costly and detrimental to a person's employment status!!!!

Find someone with the proper experience, qualifications and certification; let them provide professional and reliable data for the project.

 

[NJ1]

FFPI is right. My numbers where just for guidance and not actual facts. Just do what you thinks is rights but do not undertake something you are not qualified to do.

 

[chicopee]

To determine if you need a fire pump, you should determine the water availabilty of the street fire hydrants and details of the municipa piping size.
You could have your property fire insurance do such test or go to the water department and find out if it has a record of such test.
Following the result of such test, then you will need the experience of a professional such as your fire insurance company inspector or their own specialist. If there is no one qualified within the insurance company, then you'll need outside professional help.
It does not appear that you have the experience to carry a sprinkler evaluation which is not difficult if you have the right graph paper, initial size of feed line between street water main and sprinkler valve, sprinkler line sizes and spacing, piping arrangement etc...

 

[LCREP]

"The highest point for the building is about 32ft.The warehouse should be Ordinary hazard Group 2, and the display center is light hazard."


32' ceiling, I hope this is not the warehouse?? Ordinary Hazard Group 2 is only good for 5-12' storage depending on the commodity classification. BUT given he is asking US if he needs a pump I can only assume he has no clue about commodity classification and warehouse fire protection.




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Fire Sprinklers Save Firefighters’ Lives Too!

 

[chillylulu]

1. Building size has very little to do with whether or not you need a fire pump. I recently looked at a 2500 SqFt tire installation shop that had a water demand (flow) greater than a 1.8 million sqft high rise that I am currently evaluating. The high rise has a 1000 gpm demand, most modern warehouses have a demand of 1400 gpm to 2000 gpm. The same gpm is required whether the warehouse is 5,000 sqft or 500,000 sqft. The pressure required would be the same also, all other variables being equal (building height, hazard, storage configuration, main length, etc.)

2. Fire pumps are needed where water supplies are inadequate. Evaluation of the water supply not only includes the flow information (Static Pressure & Residual Pressure at some Flow) but also the available amount of water for fire protection use. In other words, you could have 150 PSI Static with 140 PSI @ 1500 GPM flowing, but if the supply was only good for 10,000 gallons, you would need a pump and water storage. Small pumps are routinely installed in single family homes, with a demand of 50-60 gpm. (13D)

3. Many jurisdictions would require more than Ord GP II for the storage, and the display center at first look seems to be mercantile - which is ordinary GP II.

4. You could be doing your client a huge dis-service by specifying an ordinary group II density in an area with 32 ft. deck height. The building would have very limited use if they were to re-sell later. I always try to consider an exit strategy at first look and at least give the client the option. Little or maybe no extra installation cost could result in a lot of building value.

5. Pipesandpumps is right, these basic questions show that you are in over your head. But, maybe you are just concerned with budgeting or you are checking on something you have been told, or whatever, so, to answer your questions... #1 Most likely not, but maybe. #2 Not usually, but maybe.