First of all to answer the question about what happens when a pump upstream of the operating fire pump system is also drawing water and the fire pump system has an open and flowing bypass system one just needs to go back to basic hydraulics. Where the fire pump discharge piping joins back to the bypass piping the pressures in the fire pump discharge and bypass discharge have to be equal in both pipes, period. That pressure is whatever the municipal supply can provide for the total flow to that point. In other words the fire pump cannot be operating on its curve at a discharge pressure higher than the municipal supply because if it were then the bypass check would be closed to prevent the fire pump from pumping in a circle through the bypass. Start with the flow condition of the fire pump operating with water flowing somewhere but not at a site hydrant. The fire pump is sitting on its pump curve somewhere at a discharge pressure higher than the municipal supply, and so its bypass check is being held closed. It can only be sitting on its curve since that is what a centrifugal pump does. A site hydrant is now opened with water flow. Flowing more water the fire pump rides its curve according to the total flow. Its discharge pressure goes down and will keeping going down as more water is drawn from the site hydrant, which as we should now understand can only flow as the municipal supply flows when the fire pump rides its curve down to where the municipal pressure equals the fire pump discharge pressure. Note that the water pressure in the system at this time would be less than what the building sprinkler system design pressure is supposed to be because the municipal system is flowing more water than the demand for which the fire pump was selected. The water pressure at the hydrant is at whatever it is and may or may not be being boosted by a fire department pump, but that pump has no bearing to this system hydraulics, so forget about it. We already know, from being told, that the site hydrants are perfectly fine by themselves. Now you can see that the situation is not hydraulically different from the more typical setup where a building fire pump system draws from a site hydrant system. That fire pump system would have been selected based upon the sprinkler demand and some external hose allowance affecting the supply pressure. The sprinkler system would be affected by increasing site hydrant beyond that of the external hose allowance and we would be thinking nothing wrong about it. The fire pump setup here does add additional ways to interrupt the site hydrant situation via valves in the pump bypass and the general need for system maintenance that could shut off water during times of an extreme maintenance procedure. AKS
> On Apr 23, 2021, at 11:06 AM, Steve Leyton via Sprinklerforum > <[email protected]> wrote: > > Let's change the context to a similar demand scenario where a wet-manual > combined standpipe/sprinkler system requires a pump to meet the sprinkler > demand. In that case, the pump can be sized for sprinklers only as the > primary water supply for the standpipe demand is pumped to the FDC. In > this case, you said that there is a bypass from city water around the pump: > does the city water supply meet the hydrant demand in this configuration? If > yes, then you do NOT have to size the pump for hydrant flow because the pump > isn't the primary water supply for the hydrants. They will over-perform if > the pressure in the discharge main drops during a hydrant flow scenario and > the pump kicks in because it will pressurize the line to its rating - this is > a good thing. But you do not have to size the pump for the hydrants if the > primary (city) water supply can meet the demand. > > > The foregoing is my opinion only and does not represent NFPA or the NFPA 13 > and 24 Technical Committees, nor is intended to serve as an interpretation of > the standard. > > > Steve Leyton > Protection Design & Consulting > San Diego, CA > > > > > > -----Original Message----- > From: Sprinklerforum [mailto:[email protected]] > On Behalf Of Gregg Fontes via Sprinklerforum > Sent: Friday, April 23, 2021 7:51 AM > To: [email protected] > Cc: Gregg Fontes <[email protected]> > Subject: RE: [EXTERNAL] Fire Pump Sprk & Fire Flow Demand > > So NFPA 13 11.1.5.3 does require the fire pump to be sized for the demand > that is on the discharge side of the fire pump regardless of whether it is > site demand or fire sprinkler demand or both. If the fire pump is supplying > both a 2000 gpm site demand and 900 gpm fire sprinkler demand, the fire pump > would have to be a minimum of 2000 gpm. (2000 gpm x 150% + 3000 gpm). > Correct? > > My original question wasn't meant to determine if site and fire sprinkler > demands need to be added together. Just if a fire pump supplies both per > NFPA 13 11.1.5.3, then fire pump gpm has to be able to meet both not just the > greater of the two. > > Thanks, > Gregg Fontes > Cen-Cal Fire Systems, Inc. > 209-334-9119 > > -----Original Message----- > From: Sprinklerforum <[email protected]> On > Behalf Of Bob Caputo via Sprinklerforum > Sent: Friday, April 23, 2021 6:21 AM > To: [email protected] > Cc: Bob Caputo <[email protected]> > Subject: Re: [EXTERNAL] Fire Pump Sprk & Fire Flow Demand > > Lots of great responses to this question, the best of which is that it is > really up to the local AHJ to determine what will be required. That said, in > the context of NFPA 13 (2016 edition) we should note two specific applicable > sections in consideration of the issue: > > First, section 3.8.2.1.3 defines a private fire hydrant as a valved > connection on a water supply system having one or more outlets and that is > used to supply hose and fire department pumpers with water on private > property. [24, 2013] Second, and most important to the question is section > 11.1.5.3* which requires pumps shall be sized to supply the equipment that > they serve. > > > The issue of fire flow is interesting and separate because it requires a > volume of water at 20 psi, based on the construction type and size of the > building, which can be reduced by 50% for a sprinklered building. The point > is that the fire pump cannot make water and can only provide pressure. If > your volume is not met, you’ll need a water storage tank and a pump. (Both of > which are required to be sized for the equipment they serve). > > The private hydrant is likely required because the public hydrants on the > street are too far from the rear of the building for normal hose lays and the > friction loss per 100 ft of hose is about 29 psi. Some AHJ’s require that > hydrant to become public and piped separately from the sprinkler system, with > a dedicated easement but either way, the hydrant is for fire department use > only, and they bring a pump in the engine when they show up - so its more > likely you’d need to add a water storage tank if fire flow is the concern. > Fire flow is not a NFPA 13 issue but section 11.1.5.3 is. > > Just adding my 2 cents... > > > > Bob Caputo, CFPS > President > American Fire Sprinkler Association > p: 214-349-5965 ext124 > w: firesprinkler.org <http://firesprinkler.org/> > <https://www.facebook.com/firesprinkler.org/> > <https://twitter.com/afsa/status/1039528345367732224> > <https://www.linkedin.com/company/american-fire-sprinkler-association-afsa-/> > <https://www.instagram.com/firesprinklerorg/> > > > Did You Know: Your AFSA membership entitles you to a free 30 minute > consultation with our labor attorney… Enter your apprentices to win a trip to > San Antonio! > > Deadline to enter to compete in the 28th Annual National Apprentice > Competition is April 30, 2021. Don't miss this opportunity to be recognized > for your training efforts! It’s free to enter online at > https://www.firesprinkler.org/competition > <https://www.firesprinkler.org/competition> > >> On Apr 21, 2021, at 11:51 AM, Mark.Phelps via Sprinklerforum >> <[email protected]> wrote: >> >> I've had at least one Official state (opinion) that the "Fire Flow" @ 20 >> PSI" was never intended to be "provided to the site hydrants". It is simply >> a recommendation for the benefit of Fire Fighters using their pumpers and >> hoes to "preserve" 20 psi in the city water main for all the obvious >> reasons. Ive also has fire fighters tell me that if they know its only a >> structure fire, (no occupants) they will not pull their suction pressure >> down below 20 psi. However, if there are known lives at stake, they will go >> negative on the suction pressure if they feel its necessary. >> Mark at Aero >> 602 820-7894 >> >> -----Original Message----- >> From: Sprinklerforum <[email protected] >> <mailto:[email protected]>> On Behalf Of >> Ron Greenman via Sprinklerforum >> Sent: Wednesday, April 21, 2021 9:12 AM >> To: [email protected] >> <mailto:[email protected]> >> Cc: Ron Greenman <[email protected] >> <mailto:[email protected]>> >> Subject: [EXTERNAL] Re: Fire Pump Sprk & Fire Flow Demand >> >> Consider that if the building was not there and you could meet the required >> CFC fireflow for the site you'd be done, just as you would for any land >> development project, municipal or private. No pump necessary. Then you >> reference 13 as the place with the sticky wicket paragraph about everything >> after the pump. Remember that 13 addresses sprinkler systems and associated >> hose allowances and if your site system could handle both of those without a >> pump you'd also be done. Since you apparently need a pump to meet 13 >> requirements I'd say your pump needs to be sized for the sprinkler and >> associated hose stream allowance from 13 only. But then who the hell am I? >> As Craig said, check with the approving authority. And as a bit of learned >> advice, didn't ask for a solution but rather give that person your read of >> the rules and how you got there, and then ask if that's how they see it. >> Your job is to come up with the solution and theirs is to yay or nay it. >> >> On Wed, Apr 21, 2021 at 8:40 AM Steve Leyton via Sprinklerforum < >> [email protected]> wrote: >> >>> You do not have to prove building system demand and site fire flow >>> concurrently. Hard stop. >>> >>> >>> >>> Steve Leyton >>> >>> (Sent from my smartphone; please excuse typos and voice-to-text >>> corruptions.) >>> >>> >>> >>> -------- Original message -------- >>> From: Gregg Fontes via Sprinklerforum < >>> [email protected]> >>> Date: 4/21/21 7:47 AM (GMT-08:00) >>> To: "Prahl, Craig/GVL" <[email protected]>, >>> [email protected] >>> Cc: Gregg Fontes <[email protected]> >>> Subject: RE: Fire Pump Sprk & Fire Flow Demand >>> >>> Yes. But our is CFC Section 507. What I am trying to understand is >>> NFPA >>> 13 2016 Edition 11.1.5.3 & A.11.1.5.3 "Where pumps serve some >>> combination of sprinklers, inside hose stations or outside hose >>> stations, the pump needs to be capable of providing the flow of the >>> equipment that is fed from the pump." The fire pump would be size >>> for the fire sprinkler and any NFPA >>> 13 inside and/or outside hose demands, but does it also have to be >>> size for the 2000 gpm fire flow demand since 11.1.5.3 & A.11.1.5.3 >>> states pump needs to be capable of providing flow that is fed from the pump? >>> >>> Thanks, >>> Gregg Fontes >>> Cen-Cal Fire Systems, Inc. >>> 209-334-9119 >>> >>> -----Original Message----- >>> From: Prahl, Craig/GVL <[email protected]> >>> Sent: Wednesday, April 21, 2021 7:09 AM >>> To: [email protected] >>> Cc: Gregg Fontes <[email protected]> >>> Subject: RE: Fire Pump Sprk & Fire Flow Demand >>> >>> Are site Fire Flow requirements (IFC Section 507) what you're >>> referring to as "hydrant demand"? >>> >>> At minimum, the pump should be capable of flowing the sprinkler and >>> related hose stream allowance flow rate combined. >>> >>> BUT, when there have been no municipal hydrants to be used for the >>> actual firefighting effort, we've had to be capable of providing the >>> Fire Flow rate to area hydrants plus sprinkler demand via the site fire >>> pump. >>> >>> I've also had AHJs say to only provide the sprinkler flow plus the >>> hose stream allowance via the site pump. So it really depends on the >>> AHJ as the Fire Flow requirement is stated in the code as being "by >>> an approved method" i.e., per the AHJ. >>> >>> Have you discussed this with the local fire code official yet? >>> >>> Craig Prahl | Jacobs | Group Lead/SME - Fire Protection | >>> [email protected] <mailto:[email protected]> | >>> https://urldefense.proofpoint.com/v2/url?u=http-3A__www.jacobs.com&d=DwICAg&c=wn3mZQLIuInh2ClcJ0_DIA&r=dLwiR71i_XhSFqam3ZLeaFLiQJ3cDTUB0ReB4-yDDcg&m=Bvc6gwjRPtXRrBWRivuJXEDbZbl7DWhxyJ-YGNWOf9I&s=f97kvSM5Bb0nnp19jnsS1TLlRojQT1tCyd-lF5_VfK0&e= >>> >>> <https://urldefense.proofpoint.com/v2/url?u=http-3A__www.jacobs.com&d=DwICAg&c=wn3mZQLIuInh2ClcJ0_DIA&r=dLwiR71i_XhSFqam3ZLeaFLiQJ3cDTUB0ReB4-yDDcg&m=Bvc6gwjRPtXRrBWRivuJXEDbZbl7DWhxyJ-YGNWOf9I&s=f97kvSM5Bb0nnp19jnsS1TLlRojQT1tCyd-lF5_VfK0&e=><https://urldefense.proofpoint.com/v2/url?u=http-3A__www.jacobs.com&d=DwICAg&c=wn3mZQLIuInh2ClcJ0_DIA&r=dLwiR71i_XhSFqam3ZLeaFLiQJ3cDTUB0ReB4-yDDcg&m=Bvc6gwjRPtXRrBWRivuJXEDbZbl7DWhxyJ-YGNWOf9I&s=f97kvSM5Bb0nnp19jnsS1TLlRojQT1tCyd-lF5_VfK0&e= >>> >>> <https://urldefense.proofpoint.com/v2/url?u=http-3A__www.jacobs.com&d=DwICAg&c=wn3mZQLIuInh2ClcJ0_DIA&r=dLwiR71i_XhSFqam3ZLeaFLiQJ3cDTUB0ReB4-yDDcg&m=Bvc6gwjRPtXRrBWRivuJXEDbZbl7DWhxyJ-YGNWOf9I&s=f97kvSM5Bb0nnp19jnsS1TLlRojQT1tCyd-lF5_VfK0&e=> >>> > >>> 1041 East Butler Road Greenville, South Carolina 29606 >>> CONTACT BY: email or MS TEAMS >>> >>> -----Original Message----- >>> From: Sprinklerforum <[email protected] >>> <mailto:[email protected]>> >>> On Behalf Of Gregg Fontes via Sprinklerforum >>> Sent: Wednesday, April 21, 2021 9:57 AM >>> To: [email protected] >>> <mailto:[email protected]> >>> Cc: Gregg Fontes <[email protected] >>> <mailto:[email protected]>> >>> Subject: [EXTERNAL] Fire Pump Sprk & Fire Flow Demand >>> >>> If a fire pump supplies both the fire sprinkler system and the site >>> fire hydrants, does the fire pump gpm need to be capable of suppling both? >>> (Fire sprinkler demand 900 gpm and site fire hydrant demand 2000 gpm >>> for a total of 2,900. Can the fire pump be size at 750 for the fire >>> sprinkler/hose demand or does it have to be a 2000 gpm so it can >>> supply both the sprinkler and site fire hydrant flows of 2900 gpm?) >>> The supply is city water and there is a bypass on the fire pump. The >>> city supply comes into the fire pump house and goes out to single >>> loop that supplies both the fire sprinkler systems and the site fire >>> hydrants. (The city flow and psi is adequate to meet the site fire >>> flow at 20-psi.) >>> >>> Thanks, >>> Gregg Fontes >>> >>> _______________________________________________ >>> Sprinklerforum mailing list >>> [email protected] >>> <mailto:[email protected]> >>> >>> https://urldefense.com/v3/__http://lists.firesprinkler.org/listinfo.c >>> g >>> <https://urldefense.com/v3/__http://lists.firesprinkler.org/listinfo. >>> cg> >>> i/sprinklerforum-firesprinkler.org__;!!B5cixuoO7ltTeg!XLuydu_C5h5U5xo >>> Y fFkjhto75Yz1NndsYBhU_-ghPrj9wf496LJOQnnfdGty1B3DAw$ >>> >>> ________________________________ >>> >>> NOTICE - This communication may contain confidential and privileged >>> information that is for the sole use of the intended recipient. Any >>> viewing, copying or distribution of, or reliance on this message by >>> unintended recipients is strictly prohibited. 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