# sprinkler riser question



## cda (May 17, 2011)

52000 sq ft limit on a riser

nfpa 13 says

3.5.12 System Riser.   The aboveground horizontal or vertical pipe between the water supply and the mains (cross or feed) that contains a control valve (either directly or within its supply pipe) and a waterflow alarm device.

and

The maximum floor area on any one floor to be protected by sprinklers supplied by any one sprinkler system riser or combined system riser shall be as follows:

can you have say a 75000 sq ft area that has a horizontal feed main running through it and say three floor control valves that feed 25000 sq ft each????

legal not legal?????????


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## Coug Dad (May 17, 2011)

Not legal.  Tried to do this in covered malls but were told a "riser" is different from a zone control valve.


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## RBK (May 17, 2011)

What's the difference between a bulk main with independant floor/zone controls for each system vs. a manifold arrangement as shown in exhibit 8.1 of the sprinkler handbook?  I don't know the specifics of the project, but in a typical building you would have one underground water supply, and one main "riser" pipe entering the building and then a manifold to 3 separate sprinkler systems.  The bulk main just puts the floor/zone controls at different locations in the building.


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## Coug Dad (May 17, 2011)

RBK

I don't disagree with you.  This came up on covered mall projects where we could run horizontal bulk mains with take offs for each 52,000 square feet.  The NFPA ruling was that you could not do this.  There may be a formal interpretation or handbook discussion.

By NFPA 13 definition, a "riser" is a vertical pipe.  A horizontal main is not a riser.


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## RBK (May 17, 2011)

Coug Dad,

I haven't seen anything like that in the handbook.  Do you know the rough time frame of that ruling?  Was it formal, or informal?  I can probably track it down if it was formal.

It would be interesting to see the thought process on that decision.  The 2007 handbook had a supplement about combined sprinkler/standpipe systems that would seem to advocate the use of one "system" for an entire building that is split up with floor/zone controls taken from the standpipes to maintain system protection area limits.  There isn't much difference between the supply piping for a standipe and a bulk main.  I wonder if the ruling your case had more to do with a "bigger picture" approach because it is a mall.


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## Coug Dad (May 17, 2011)

By NFPA 13 definition, a "riser" is a vertical pipe. A horizontal main is not a riser.


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## cda (May 17, 2011)

3.5.12 System Riser. The aboveground """"""   horizontal """""""or vertical pipe between the water supply and the mains (cross or feed) that contains a control valve (either directly or within its supply pipe) and a waterflow alarm device.


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## cda (May 17, 2011)

RBK

Would you say do a 70000 sq ft non high piled warehouse with one riser and on floor control valve off that riser to split it so you have say 52000 off the main riser and a tap off a main down stream with just a valve and flow switch to feed the other 18000 sq ft ??


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## RBK (May 17, 2011)

Coug Dad said:
			
		

> By NFPA 13 definition, a "riser" is a vertical pipe. A horizontal main is not a riser.


Correct.  But a vertical pipe isn't the only piece that defines a system riser, either.

I would say that in the case described by CDA, the bulk main running through the building to the separate floor controls meets the letter of the NFPA 13 requirements, though maybe not the intent as described in Coug Dad's experience with the mall.

If I were to review the system, I would have a hard time finding a code section to cite in rejecting the proposed arrangement.  Without some kind of direct input from NFPA clarifying the intent, I would say the system is legal.  That said, if I had a problem with the arrangement, I would work with the designer to see what could be done to fix the problem.


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## RBK (May 17, 2011)

cda said:
			
		

> RBKWould you say do a 70000 sq ft non high piled warehouse with one riser and on floor control valve off that riser to split it so you have say 52000 off the main riser and a tap off a main down stream with just a valve and flow switch to feed the other 18000 sq ft ??


It's all about what is downstream of the control valve.  As soon as you have a control valve (and flow switch), you have a system riser.  The system downstream of that can protect no more than 52000.  If you take a bulk line off the floor control pipe, before the control valve (so before it is really a system riser) and run that bulk line 10' away (or to the other side of the building, as is implied in this case) and take another floor control off that to protect the remaining 18000, you meet NFPA 13 requirements.


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## cda (May 17, 2011)

Rbi

If the set up you described below was submitted to you and it had 70000sq ft on one floor one riser with floor control valves to break down the sq ft

You would say it meet the 52000 sq ft limit per one riser because it had the seperate control valves to break down the sq ft



			
				RBK said:
			
		

> Correct.  But a vertical pipe isn't the only piece that defines a system riser, either.  I would say that in the case described by CDA, the bulk main running through the building to the separate floor controls meets the letter of the NFPA 13 requirements, though maybe not the intent as described in Coug Dad's experience with the mall.
> 
> If I were to review the system, I would have a hard time finding a code section to cite in rejecting the proposed arrangement.  Without some kind of direct input from NFPA clarifying the intent, I would say the system is legal.  That said, if I had a problem with the arrangement, I would work with the designer to see what could be done to fix the problem.


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## RBK (May 17, 2011)

That would be my opinion.  The system size limitation exists for 2 reasons:  to limit the size of systems, and to limit the area left unprotected if the system is out of service.  You have achieved the second goal, at least as much as practical, by dividing the building up with 3 systems.  A break in the incoming water supply still takes out the whole building, but NFPA doesn't specifically address that.  As for the limit on the size of the system, I haven't found any other guidance from NFPA on their limit on system size.  I would be really uncomfortable with 1,000,000 sq. ft. with only one water supply, but not too concerned about 70000.

On a side note about system size, I see the system size limit as somewhat self regulating.  It's interesting to note that FM no longer has an area limit on sprinkler systems.  If you can't get the calcs to work, the system is too big.


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## peach (May 17, 2011)

comes down to the hydraulic calcs.. like many of the NFPA codes, you need to unthink what you think you know and read NFPA 13 - terminology is frequently different.


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## cda (May 17, 2011)

Peach

So you have no problem with going over 52000 sq ft

If I read you right


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## Builder Bob (May 18, 2011)

Yes - legal.

The feed is not limited to the amount of area that it can protect........ the riser has to be designed so that no area greater than 52,000 SF will be out of service at one time.  Not any different than having one riser serving 10 floors of 52,000 SF. The limitation is per story - not accumulative area coverage of all floors combined.


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## cda (May 18, 2011)

builder

but if you shut down the one riser feeding the one fire area of over 52000 sq ft, even though you have sections controlled by floor control valves, you shut down over 52000 sq ft


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## RBK (May 18, 2011)

cda said:
			
		

> builderbut if you shut down the one riser feeding the one fire area of over 52000 sq ft, even though you have sections controlled by floor control valves, you shut down over 52000 sq ft


I think I misunderstood your earlier description of the system.  I agree that having a valve shut off the entire building (over 52000) is not legal per NFPA.  Though, realistically it is legal to have a PIV or OS&Y on the backflow that would accomplish the same thing, so I don't see a whole lot of difference.

To keep it legal, you would need bulk pipe into the building, with 3 separate floor controls attached to the bulk pipe.  No control valve on the bulk pipe, but a drain and flow switch would be a good idea.  If they have a floor control for 52000, then take another system off of one of the feed mains within that system, then that is illegal.


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## cda (May 18, 2011)

RBk

You got it

We think we convinced the company the design was not to 13

Hay but you see new things all the time


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## Builder Bob (May 19, 2011)

[/img] Hortizontal Feed and Vertical Feed Automatic Sprinkler system (N.T.S.)

Information is for discussion purposes only.

Details omitted for simplistic discussion concerning control/zone valves. Details such as FDC, tampers, flow switches, retard chambers, etc. omitted.


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## FM William Burns (May 19, 2011)

I couldn't take it anymore and was going to sketch it too.........thanks BB


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