Does 175 psi Limit Apply at FDC for Standpipes?

11/23/2022

NFPA-14 2019 Edition. There is a new section in NFPA 14 - Section 7.8.1.2.1:

The pressure required at the fire department connection for manual standpipes shall not exceed the working pressure of the system components of the standpipe system or sprinkler system when the system is a combined system.

Does anyone have any idea why this was added?

It seems to me that the maximum pressure at the FDC would be 175psi as this is what the sprinklers are rated.

Pumping at that pressure I would never get the 100psi required at the top of the most remote riser.

Or am I interpreting this section incorrectly?

Thanks in advance.

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12 Comments

Dan Wilder

11/23/2022 07:43:31 am

My best guess (and I've done this before using 200PSI on a 750GPM combined standpipe) and needed 180 at the base.

NFPA 1901 for Fire Pump Trucks and their pump ratings has information up to 250PSI. A designer could use the higher rating to keep a manual standpipe fed via FDC vs having to go to an automatic standpipe and incur the cost of a pump. Truck engineers don't really care about (at least it's not the primary thought) component rating, if the hose guys ask for more pressure, they are getting more pressure.

It's in PI 34 - https://www.nfpa.org/assets/files/AboutTheCodes/14/14_F2018_SPI_AAA_FRReport.pdf

Public Input No. 34-NFPA 14-2016 [ New Section after
7.8.1.2 ]
7.8.1.2.1
The pressure required at the fire department connection for manual standpipes shall not
exceed the working pressure of the system components of the standpipe system or sprinkler
system when a combined system.

Statement of Problem and Substantiation for Public Input

Some contractors have been calculating all 4" standpipe systems and bulk to the FDC and
indicating that the PSI required at the FDC is IE: 245 PSI. (Report from Denver). This is on non
high rise combined systems. The PSI required at the FDC should not exceed the pressure
ratings of the system components for manual standpipes.

Dwight Havens

11/23/2022 08:31:14 am

Essentially, this means that if the standpipe is combined with a fire sprinkler system, and the required pressure to operate the standpipe is greater than 175 psi, the components of the sprinkler system that are not rated for pressures greater than 175, need to be upgraded. This is one reason that sprinklers listed to pressures greater than 175 psi were developed. The alternate is to pipe the sprinkler systems and standpipe systems separately.

Alex

11/23/2022 08:41:13 am

NFPA 14 (2019) 7.2.1 states the "maximum pressure at any point in the system at any time shall not exceed 400 psi".

Therefore, if you have a standpipe system protected with PRVs, you are allowed to pump at greater pressures. You need to ensure that any component not rated for pressures above 175 psi is installed downstream from a PRV to prevent failure.

Matthew King

11/23/2022 01:03:18 pm

If you put in PRV and have an overpressure event., you will not have fire protection. That violates fundamental precepts of code, protect life and property, noting life is first. That's why they limit source pressure to the pressure of the lowest rated pressure of any component in the system. Another way to look at it, if you need more than 175 psig, then you have designed outside of code - look at you hydraulics ( pipe size) and zone design, adjust accordingly.

Jonathan Joseph

11/23/2022 09:27:57 am

For a manual standpipe system the maximum floors you would exceed in height is typically 8 stories just below the 75 feet so to get a 100 psi residual pressure on the roof or top landing you can keep all components on any part of the combined system under 175 as long as the fire pumper operator does so.

DAVE

11/23/2022 11:02:18 am

I haven't gone back through the committee discussions, but in AFSA Russ Bainbridge's January 7 article for "Sprinkler Age" on 2019 changes to NFPA 14, he states:

• Section 7.8.1.2 removes the wording “topmost” and replace it with “of the hydraulically most remote 21/2-in. (65-mm) hose connection valve.” This should help alleviate some confusion when calculating the system to clarify the most remote outlets should be calculated.

• Section 7.8.1.2.1 is being added which opens the door to manual system designs that exceed 175 psi inlet demand.

– “The pressure required at the fire department connection for manual standpipes shall not exceed the working pressure of the system components of the standpipe system or sprinkler system when the system is a combined system.”

• Sections 7.10.1.2.1 and 7.10.1.2.2 remove the wording “topmost outlet” and replace it with “connection point.” This should help alleviate any confusion about whether NFPA 14 is requiring two 21/2-in. outlets to be installed at the top of standpipe systems and which outlets should be calculated.

https://www.sprinklerage.com/nfpa-14-2019-edition/

Kelsey

11/23/2022 11:15:08 am

And it might be below 175psi as well. If my FDC is at ground level, but my systems go below ground, I might have to have a maximum of ~150psi at the FDC.

Eric R

11/23/2022 11:46:49 am

This is one of those code sections that shouldn't need to exist, but does because someone messed up a design using way to much 4" pipe, and then tried to rules lawyer their way out of the mistake by saying this very requirement wasn't explicitly stated in the code.

My state has gone even further and limited the max pressure at the FDC to 150psi for manual standpipes.

I just ran a super quick calc on two 70' tall standpipes separated horizontally by 130'. The demand comes out to 750gpm @ 150psi even when both 70' risers are limited to 4" pipe, with 4" pipe running the 130' distance between the two risers, and only utilizing 6" for the common piping from FDC to the first standpipe tee,

Obviously an abstract layout, but it really shows that there is no good reason to design a manual standpipe that needs pressures higher than 175 psi.

Mark Bagniewski

11/23/2022 12:17:23 pm

One reason this could have been added is for the firefighting side of the system. Depending on the jurisdiction, the FDC is either going to be a 2.5” connection, or a 4/5” stortz connection (large Diameter hose). One of the big issues with LDH is that they only have a service rating of 225 psi max. That rating is more for the actual hose. The weak point of the hose is the stortz connection to the hose. When you operate LDH at that sort of pressure, the hose normally does fine, but the hose will blow off the connection, and send the hose flying.

As for the 2.5” connections, these hoses can operate at higher pressure, but the stress of the hose weights and gravity pulling on these FDC connections at a 90 degree angle a few feet off the ground with connections that are usually just left outside in weather with little protection can also fail.

Just speculating as to why it might be added.

And PS as an FPE and a fire officer, we do enjoy speaking to the FPE when they design buildings in our area. The more information you can provide us in regards to your design, the better off we can utilize the systems when needed. And that goes for the guy pumping into your system, the guys hooking up to your system, and the fire officers managing the incidents and utilizing your systems.

Danial Bartle

11/28/2022 12:37:28 pm

When I was at the FD, the LDH was never supposed to be used for anything other than supply to the truck from the hydrant. They started adding 3" intake pipe and Stortz connections to pump the hose primarily to set up a relay from distant water supplies and the pressure was always 150 psi for the maximum flow of the pump. I haven't kept up with the NFPA requirements for fire hose but I would hope the pressure tests of the 4 and 5" hose has been adjusted for increased pressures for Stortz connections at FDC's.

Danial Bartle

11/28/2022 12:39:22 pm

Sorry, "intake" should be spelled "discharge".

Anthony

12/5/2022 12:18:06 pm

This one is always hilarious to me on several levels:

If the fire truck can produce 200 psi you can best your bottom dollar in an emergency all 200 are going to be used.

Also we test the sprinkler system at 200 psi. So what every sprinkler is invalidated for use or has experienced over pressure before the system is put into service? Obviously the components can withstand higher pressure than they are 'rated' for. I think most sprinklers are tested at 300 psi at the factory?

175 always just seemed arbitrarily less than the test for the system.

Also funny to me is that any time the fire department hooks up to a manual system and over pressurizes it the relief valve will start flowing. This may prevent the most hydraulicly remote valve from getting all the pressure it requires.

Does 175 psi Limit Apply at FDC for Standpipes?

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