fire water demand

[Cris-w]

hi everyone
I have a newly built steel plant building equipped with standpipe system、automatic sprinkler system, and outdoor fire hydrant system. How should I determine the maximum water demand of this building? Should I add up the water demand of each system? Especially, how to determine the water demand of the outdoor fire hydrant system?
Advance thanks！

 

[UFT12]

It should be in your fire code. See for example NFPA 1, chapter 18.

 

[Cris-w]

It should be in your fire code. See for example NFPA 1, chapter 18.

I'm very sorry. After reading NFPA 1, I feel that it doesn't clearly specify this. Maybe I just didn't notice it. Could you give me some more hints? Thank you.

 

[cdafd]

So the building is already built and in operation???!

If so why the question

 

[Cris-w]

So the building is already built and in operation???!

If so why the question

No, it's just that the construction has just started, but now we need to select the specifications of the fire pump. I haven't found any instructions on how to calculate the flow rate of the fire pump in NFPA. I'm very anxious and hope to get some help.Thanks a lot.

 

[SprinklerDesigner2]

I hold a NICET IV in fire sprinkler layout with 50 years experience.

While I know what fire flow is and means I would NEVER do the calculations because it isn't my job.

The responsibility of calculating fire flows is the job of the registered architect, licensed civil engineer or professional engineer on the facility and not the fire sprinkler designer for the project.

I have seen different states do it differently and I just don't want to go there.

From NFPA https://www.nfpa.org/news-blogs-and-articles/blogs/2022/03/22/calculating-the-required-fire-flow

 

[Cris-w]

I hold a NICET IV in fire sprinkler layout with 50 years experience.

While I know what fire flow is and means I would NEVER do the calculations because it isn't my job.

The responsibility of calculating fire flows is the job of the registered architect, licensed civil engineer or professional engineer on the facility and not the fire sprinkler designer for the project.

I have seen different states do it differently and I just don't want to go there.

From NFPA https://www.nfpa.org/news-blogs-and-articles/blogs/2022/03/22/calculating-the-required-fire-flow

soory，you mean to determine the flow rate of the fire pump based on this?

 

[cdafd]

What is your occupation?

There are to many variables to get an answer here.
You have to figure fire flow for the building, water supply either public or tank or other, fire sprinkler system demand. Not sure why a standpipe is involved.

 

[Cris-w]

What is your occupation?

There are to many variables to get an answer here.
You have to figure fire flow for the building, water supply either public or tank or other, fire sprinkler system demand. Not sure why a standpipe is involved.

I am mainly engaged in the fire protection design of power plants. According to NFPA 850, the water supply demand is calculated by adding 500 gpm to the flow rate of the largest system. However, this is a steel mill, and I haven't found the specific requirements of NFPA for it.

 

[SprinklerDesigner2]

What is your occupation?

There are to many variables to get an answer here.
You have to figure fire flow for the building, water supply either public or tank or other, fire sprinkler system demand. Not sure why a standpipe is involved.

I am not qualified to answer this question but here goes anyway from the way I understand it to be.

What matters the size of the building and if the building/property has sprinklers. If the building has sprinklers the fire flow might be 1,000 gpm if if the building is not sprinkled the fire flow might be double to 2,000 gpm. The way I understand it is it has nothing to do with the sprinkler design, the number of systems or if it has a standpipe or not.

Maybe try this https://www.omnicalculator.com/construction/fire-flow

 

[Lucas An]

Key Considerations
Simultaneous Use: NFPA 1 requires the water supply to meet the maximum combined demand of all systems operating together.
Hydrant Fire Flow: Represents manual firefighting efforts and is calculated separately but often reduced for sprinklered buildings.
Standpipe vs. Hydrants: Standpipes (internal) and hydrants (external) are distinct; their demands are typically additive.
For precise compliance, consult NFPA standards and local fire codes.

 

[cdafd]

Is this in the U.S.?

Do you know a fire protection engineer, that knows hydraulics, that can help you

 

[TravisMack]

I highly suggest you contact a competent fire sprinkler contractor or a competent fire protection engineer. Site fire flow, standpipes and sprinklers are individual demands. They are not required to be compounded, unless you have an authority (local code enforcement, insurance, etc) that requires it. Typically, fire pump capacity is going to be driven by the site fire flow demands. Pump rating will be typically driven by the standpipe pressures or sprinkler system pressures, whichever is greater.

However, you really need to engage the help of a licensed professional that you are paying for their advice. If you are tasked with doing this work, it would not be my recommendation to take it from some forum online.