Why is a Hose Allowance Required?

8/2/2023

I have a question in regards to hydraulic calculation and hose stream allowance being added to the calculations.

When and why are they added to your hydraulic calculations?

Is this specifically required under NFPA 13 somewhere regardless if a standpipe is required or provided?

Any insight or clarification would be greatly appreciated.

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9 Comments

Pete H

8/2/2023 06:34:38 am

https://www.hsdl.org/?view&did=721443

This coffee break training explains it well enough:

"“Hose stream demand” is the amount of water that must be added to the sprinkler system hydraulic calculations so there is adequate supply to operate the sprinklers for effective fire control, and fill the hoses for fire extinguishment."

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So basically, if the fire department is connected to the same system/hydrant/water source, that there's enough flow and pressure in the system to let them do what they have to do, and let your system do the same.

Pete H

8/2/2023 07:47:19 am

Realize I never answered the "when are they added to your calculations" part of the question.

Typically, at your source node.

It is specifically required under NFPA 13 regardless of whether or not your have a standpipe.

Anthony

8/2/2023 08:07:41 am

Is hose stream required by NFPA 13? Yes, NFAP 13-2016 CH 11.1.6 Hose Allowance. It is required regardless of standpipe inclusion in the building.

When hose allowance is included: anytime the sprinkler system and the hose demand come from the same source. If for some reason there is no hose connections available you'd omit that from your calculations. see A11.1.6.2

Dan Wilder

8/2/2023 08:10:17 am

My understanding for hose allowance

It sets up the property with a properly sized sprinkler system using an adequate water supply (sprinkler demand + hose stream or standpipe demand, whichever is greater) for the required duration based on what section of NFPA is applicable. The calculations only add GPM to the design, not any actual pressure requirements (likely due to a responding department having the ability to supplement pressure).

NFPA 13-22' - 19.2.3.1.2 (Light, Ordinary, Extra Hazards)
NFPA 13-22' - 20.15.2.6 (Storage)
When there are interior hose stations (1½ or 2½), the 50GPM per location, up to 100 GPM becomes the "Inside Hose" Allowance. If there are no interior hose valves, that number is 0. Then the remaining total hose allowance is accounted for with the "Outside Hose Allowance".

Make sure to check out 13-22 - 19.1.6.3.1 for only outside hose allowance within fully sprinklered building that has a combined sprinkler/standpipe application.

Big remember item, pumps (on a fire truck or a fire pump) cannot add GPM to the equation, only PSI.

Mort

11/2/2023 02:39:57 pm

Does this mean that for a storage design you add to the sprinkler demand the 50 gpm where it connects to the sprinkler system (up to 100 gpm) and then your outside hose allowance becomes 400 gpm?

Jesse

8/2/2023 08:18:05 am

Hose allowance is indeed required by 13. It ensures that the system is designed and calculated to the anticipated water supply characteristics when the fire department is pulling water from the same system that feeds the AS system.

Glenn Berger

8/2/2023 08:24:02 am

As stated above, hose streams are required to be added to the sprinkler system hydraulic calculations. The hose allowance is added to the calculations where the fire department will connect into the system. This could be either or both a standpipe and/or nearest fire hydrant.

The reason to add fire hose allowance is that the fire department will be utilizing their hoses concurrently with sprinkler system flow.

Adam

8/2/2023 08:53:16 am

Also to note, that hasn't been mentioned yet - When there are indoor hose stations, and the water for both sprinklers and standpipes come in on the same service line, include the indoor hose allowance volume through the incoming line up to the point where the systems branch apart from each other.

Ken

5/31/2024 11:32:07 am

It is my understanding that hose allowance is not required to be added to calculation in high rise building when a fire pump is fed from water storage tank and handling both the standpipe and sprinkler system demand. Is this correct?

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Why is a Hose Allowance Required?

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