Sprinkler Supply line

[JoeWill123]

What NFPA standard tells me if the fire main must be 6 inch or 4 inch to for the purpose of a new suppression system in a facility? How do I know if a 4 inch is permissible? VS. the 6 inch



Joe G. Willett
Jacksonville, AR

 

[LCREP]

NFPA 24, Standard for the Installation of Private Fire Service Mains and Their Appurtenances,2007 same as 2002 edition

5.2 Size of Fire Mains.
5.2.1 Private Fire Service Mains. Pipe smaller than 6 in. (152.4 mm) in
diameter shall not be installed as a private service main suppling
hydrants.
5.2.2 Mains Not Supplying Hydrants. For mains that do not supply hydrants,
sizes smaller than 6 in. (152.4 mm) shall be permitted to be used subject
to the following restrictions:
(1) The main shall supply only the following types of systems:
(a) Automatic sprinkler systems
(b) Open sprinkler systems
(c) Water spray fixed systems
(d) Foam systems
(e) Class II standpipe systems
(2) Hydraulic calculations shall show that the main is able to supply the
total demand at the appropriate pressure.
(3) Systems that are not hydraulically calculated shall have a main at
least as large as the riser.

 

[JoeWill123]

thank you...........is there a maximum length that a 4 inch or 6 inch can be? 500 feet? 1000 feet?

Joe G. Willett
Jacksonville, AR

 

[TravisMack]

Joe,

The length is simply dependent upon what is supported by calculations. There is no maximum length mandated by NFPA 13 or 24.

Travis

 

[ChrisConley]

LCREP,

If the fire main is a combined building service line, would the hydraulic calculation have to take in to account domesitc water usage?

In my mind, if the sprinklers are discharging the building should be evacuated or evacuating... not a lot of showering and toilet flushing.

Thanks,

 

[cdafd]

2) Hydraulic calculations shall show that the main is able to supply the total demand at the appropriate pressure.

The main can be smaller than six inch

yes you need to add domestic use, it may be a business that uses alot of water for a process.

 

[JoeWill123]

Thank you so much for all the great inputs; are there any "simple" and "easy" books or formulas I can use to give me a ball park estimate of required water supply ?

Joe G. Willett
Jacksonville, AR

 

[ChrisConley]

I've never seen domestic use taken into account during the hydraulic design of a combined fire/domestic water main. I've also never seen a main smaller than 6" installed.

I've read NFPA 24 and don't see any guidance on domestic water usage. Again, is it pratical to assume a large number of toilets are being flushed in the facility during a fire?

I can see taking into account the process requirements of an industrial facilty.

 

[cdafd]

do not have nfpa 13 with me but it may be in there

 

[gouveia]

NFPA 13 (2002 edition)

A.15.2.1 Care should be taken in making water tests to be used in designing or evaluating the capability of sprinkler systems. The water supply tested should be representative of the supply that might be available at the time of a fire. For example, testing of public water supplies should be done at times of normal demand on the system. Public water supplies are likely to fluctuate widely from season to season and even within a 24-hour period. Allowance should be made for seasonal or daily fluctuations, for drought conditions, for possibility of interruption by flood, or for ice conditions in winter. Testing of water supplies also normally used for industrial use should be done while water is being drawn for industrial use. The range of industrial-use demand should be taken into account. In special situations where the domestic water demand could significantly reduce the sprinkler water supply, an increase in the size of the pipe supplying both the domestic and sprinkler water can be justified.

I believe the new 2007 edition added additional wording to accommodate domestic demand. However, I don't have ready access to the code yet.