Fire water demand and pressure

[cabalen]

Can anyone help me estimate the fire water demand and pressure required for an office building. We need this info as preliminary interface data for utility requirement.

Any information is highly appreciated.

Thanks.

 

[TravisMack]

If it is just simply an office building with ceilings <10', metal building and no storage, wet pipe system & quick response sprinklers, the flow could be as low as 100 gpm interior demand and a hose allowance of 100 gpm.

If you have a wood structure with slopes >=4:12, you could have a demand of 500+ gpm interior and 100 gpm hose allowance.


The pressures could be as low as 25 psi at the base of the riser for the wet system and around 50 psi at the base of the riser for the dry system. All of the pressures can be modified with pipe sizing.

So, as you can see, more information is needed to get what you want.

 

[cabalen]

Thanks TravisMack,your info is helpful but we would like to provide maximum values for gpm and pressure because this is for conceptual study so, I think the maximum is better.

Please consider the building as a 3-storey, Security building with an armory section. Would the armory room would affect the water demand and pressure?

I have read from a fire pro reference that the maximum gpm for Ordinary hazard application based on Pipe schedul is 1500 gpm and the maximum pressure for fire pro sysytem is 95 psi. I just would like to hear some comments from experienced people on this.

Any info is appreciated.

Thanks.

 

[TravisMack]

Stored ammunition is a Class IV commodity. Being a 3 story building, I would assume that your storage for the ammunition would be less than 10' in height. Therefore, you could be at Ord Grp II requirements. For a wet system, you could be at a minimum of 300 gpm + 250 gpm hose allowance. Practically, you can figure about 15% overdischarge from the sprinkler system and have 330 gpm + 250 for a total of 580 gpm. Pressures are all dependent on the pipe sizing and sprinklers chosen. You could probably get by with 50 psi or so at the base of the riser.

Don't even consider pipe schedule stuff for you application. It is very likely that you would not be allowed anything with a pipe schedule and would require a calculated system.

Good luck!!

 

[cabalen]

Thanks again Travismack, I have specified 750 gpm and 95 psi. I included some allowance since this are assumed values and they are subject to change during detailed design.

What would be the size of the main FW pipe for the above specs?

Thanks.

 

[TravisMack]

You could likely bring that in with a 6" line, depending on how far you have to run the fire line from the city tap.

 

[cabalen]

Thanks TravisMack for being helpful and sharing your thoughts.