Long question - in essence - is Fire Flow considered on top of a flowing sprinkler system?

Recently there was a great discussion on the forum here about whether a water storage tank size needs to include Fire Flow in addition to sprinkler demand. There were some great points made (www.meyerfire.com/daily/must-water-storage-tank-include-site-fire-flow).

I have just come upon a project where we do have a municipal water supply, but it tapers off very steeply. The flow test in the area was 52 psi static, 25 psi residual at only 650 gpm. This would put the available Fire Flow around 712 gpm at 20 psi for the site.

In order for the AHJ to reduce the required Fire Flow under the IFC, the building(s) nearby need to be sprinkler-protected. This would bring down the Fire Flow requirement to 1,000 gpm at 2-hours, for this setup. The sprinkler system isn't designed yet, but we'd estimate around a 550-650 gpm demand with a fire pump. This gets really interesting based on the prior discussion.


When the fire department shows up on site during a fire, and then starts to pull water, is this Fire Flow in addition to the flowing sprinkler system, or considered separate?

In other words, is the 1,000 gpm (for 2 hours) for Fire Flow on top of a 600 gpm demand for sprinkler (for 60 minutes)?


If the water storage tank needs to meet the demand of the sprinkler and Fire Flow separately, then the calculation comes down to ~300 gpm needed to fill the shortage on Fire Flow, multiplied by 2-hours. That's a tank in the ballpark of 35-40,000 gallons.

If the water storage tank needs to meet the Fire Flow as the sprinkler system is operating, that's a flow of around 1,600 gpm to fight a fire. That's as much as ~900 gpm x 2 hours to a ballpark of 100-115,000 gallons. Huge difference.


I can't find any relevant code that stipulates one way or another, only that the tank must supply the sources it is connected to. 

Am I looking at this correctly? I see sprinkler and Fire Flow needing to be met by a tank that they're connected to, but is the Fire Flow robbing the sprinkler system, or vice-versa?

Thanks so much for reading. This is obviously TLTHFR (too long, thank-you-for-reading).

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Recently a client determined that they no longer want diesel fire pumps to be provided on their projects. They want electric fire pumps with a diesel generator to ensure reliable power. (Please do not ask why state this desire.)

If a diesel generator is provided strictly for the electric pump assembly, what mechanism do you utilize to turn the generator on when fire pump needs to start up?

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I have a standpipe demand of 750gpm. I am providing a fire pump for the system demand.

Should I be selecting a 750 gpm pump or a 1000 gpm pump, based on adding a safety factor (or other reasoning)?

My sprinkler demand is less than 750 gpm so I would only need to provide the 750 gpm for the standpipes. Thanks in advance.

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​I am currently evaluating a 7-story building that is being partially renovated and has an existing standpipe system (2 standpipes), but no sprinklers. My scope was to add sprinklers to the renovated areas, creating a partially sprinklered building.

The lack of pressure is leading the AHJ to require a fire pump due the 100 psi required for the standpipe system.

While the standpipe requires the fire pump, hydrant flow tests indicate that there may be sufficient pressure to supply a sprinkler system.

My question is two-fold. Is there really such a thing as a non-combined sprinkler/standpipe system where they are both required?

They both get their water supply from the same source.

Also, can I evaluate supplying the sprinkler system through a separate riser that tees off before the fire pump, while the fire pump supplies only the standpipe, significantly reducing the size of the pump?

The pump would be sized for 750 gpm total, 500 gpm @ 100 psi to the remote hose connections, and 250 gpm to the second standpipe.

What would that sprinkler calculation look like?

Would the sprinkler calculation remove the hose stream allowance and replace it with the 750 gpm to consider the flow to the pump/standpipes?

The flow potential is there based on the hydrant flow test just not the pressure for the standpipes (and it's close for sprinklers). I'm just wondering if I can give the client and rest of the design team options.

Thanks in advance.

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Architect here with a fire code question. We have a fully sprinklered building (ESFR), of Type II-B, tilt concrete construction.

The fire pump room is located on an exterior wall, and the only door into the pump room is from the exterior. We have 1-hr rated construction separating the fire pump room from the rest of the building.

The fire marshal is telling us that the exterior wall and door also have to be rated. I responded by pointing out the fire pump is required to be protected from the surrounding building, and that it does not need to be protected from the exterior, so exterior wall and door should not have to be rated.

Fire marshal disagrees and pointed to NFPA 20 4.14.1.1.2. That section does not specifically state that separation is required from the rest of the building, although Section 4.14.1.1.1 right before it does make that distinction, just like IBC/IFC do.

We have solid concrete walls that are inherently fire rated construction, so typically I would just say ok and label them rated. The issue is we are required to have ventilation in the pump room per NFPA 20, so we have a makeup air louver in the exterior wall. If we rate the wall, then my understanding is we will have to put a fire/smoke damper on that louver, which is added cost and unnecessary in my opinion.

Is your understanding that all walls have to be rated as the fire marshal is saying, or just the walls between pump room and rest of building?

I've done many buildings of this type in multiple states and this is the first time I've been told this. I'd appreciate your insight, thanks.

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We have a fire pump room with three 75 HP main pumps that operate sequentially depending on the flow required.

Can we install all 3 controllers within a single enclosure?

If not, what standard, code forbids this?

Thanks in advance.

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I recently obtained an annual full flow fire pump flow test data via hose monsters and pitotless nozzles to open atmosphere.

I am attempting to develop a graph from scratch in Excel for the fire pump curve or honestly, find one that is already built on line where I can plug in each data point for the Actual results (Churn, 100%, and 150%) and Theoretical/Design (Churn, 100% and 150%).

Does anyone know of such available graphs or advice on steps to develop in Excel (or a different program)?

Thank you in advance.

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We have an underground water storage tank (concrete) with two compartments; Tank 1 and Tank 2. Our fire pumps are vertical turbine type: 1 duty and 1 back-up. Both suctions of each fire pump are located only at Tank 1.

Is this code compliant?

Or shall we relocate the suction of the back-up fire pump into the Tank 2?

Thanks in advance.

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What does "listed for fire protection use" actually mean?

The Department of Defense specifications Section 21 13 13 calls for backflow preventers to be "listed for fire protection use".

From what I have found, there is no such specific listing.

Has anyone else heard of this?

Thank you for your input.

​

During fire pump testing, for the churn test, should the system valve (on discharge side of course) be open or closed?

I lean towards it being open, as I would rather know the weak point during a test than during an actual fire event.

Here's my pro/con list to keeping the valve open:

Pros (keeping valve open)

• Could be required by Insurance provider/AHJ
• Discovery of weak points in system rather than a real event
• Closed valve creates in impairment, self-performing facilities risk leaving the valve closed

 
Cons (keeping it open)

• Possible over pressurization due to incorrect fire pump settings
• Older systems with compromised underground systems could increase
• If verification of fire pump is the purpose, why subject the rest of the system to churn pressure and possible water hammer if not required

Thanks in advance!

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Does a double wall diesel tank require a reservoir?

​Thanks in advance.

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Hi everyone - thanks for answering my previous questions and for checking out today's as well.

I have three projects all connected to the same central fire pump assembly. It's a huge network of pipe running for miles. 

The client is having a problem with the fluctuating pressure (up and down) on the network for some reason that affects the fire pump's suction pressure. It's in series, and connected to each project.

The client refuses to add a break tank and cut the fluctuation. 

In your experience, is there any alternative solution available? 

Would a pressure relief valve help? What would happen when the pressure is less than design?

Thanks in advance!

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Does a fire pump on an NFPA 13D system require backup power?

It seems like it should, but 13D does not say that it has to and does not reference NFPA 20.

Thanks in advance.

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Thanks for answering my previous questions; I have another one today.

Is the life safety electrical demand on the generator, for the electrical engineer, based on the normal-duty load (346 bhp), motor load (500 bhp), or the maximum locked-rotor road (572 bhp)?

Is there a governing standard that dictates this (IFC/NFPA 20/NFPA 70)?

We have a 2,000 gpm, 185 psi rated electric fire pump. Thanks in advance.

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For a horizontal split case fire pump, 10 pipe diameters of straight pipe is to be provided for the suction inlet.

My design includes a gate valve and strainer within the 10 pipe diameters.

Is the strainer allowable in this range?

I'm unable to find in NFPA 20 any input on this. Thanks in advance.

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I have question regarding fire pump capacity.

In my situation the water department is requiring a city tap size to be 2 pipe sizes larger than the fire protection backflow preventer.

In my project, I was using a 4" backflow and 400 gpm fire pump so my underground/city tap would be required to be at least 6 inches.

The AHJ is requiring me to increase the area size in one of my remote areas. So, my sprinkler demand now becomes 582 gpm. To avoid having to use a 500gpm fire pump (with a minimum suction size of 6-inch) and increase the underground to 8-inch, could I still use the 400 gpm fire pump to supply the 582 gpm demand?

This comes out to about 145% of the pumps rated capacity.

I have never come close to the 150% mark before and just want to see what others think. If the underground size wasn't required to be 2 inches larger I wouldn't even think about it and go with the 500 gpm pump.

Thanks in advance.

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NFPA 20 says that if the test header supply main is more than 15 feet from the fire pump, it must be increased one pipe size or hydraulically calculated based on 150 percent of the rated pump capacity.

What form does the hydraulic calculation take?

Are we trying to determine if the main can flow 150 percent of the pump rating without running out of pressure?

How low a pressure would be acceptable?

Is this a one time calculation to size the main or is this a calculation that must be performed during each annual fire pump test?

Thanks in advance.

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For a fire pump subject to NFPA 20, I know that the suction side requires an eccentric reducer, but “can” one be put on the discharge side?

I have a situation where we are removing and replacing existing pumps where both the suction and discharge are at the same elevation, but the new pumps have the discharge about 2.5” lower than the suction.

I am trying to find a solution to resolve this. Thanks in advance.

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Can the pipe from a remote FDC at the front of our building route under the building slab to connect to our fire pump room at the back of the building?

The Fire Pump Room is on the basement level.

This is for a six-story hotel with a partial basement along the back portion of the building that is open to a lower grade level in back. Here's a sketch below.

The fire marshal requires a remote FDC at the sidewalk in front of the building. Our fire pump room happens to be on the opposite side, in the back.

The most straightforward routing is below the building, but it is minimum 60' of run which certainly exceeds the 10' maximum distance allowed for the fire supply from NFPA 13.

Going above the first floor ceiling is challenging given all the interiors/ceilings, public spaces, and glass at the street front.

Given that the FDC pipe is normally-dry and not pressurized, do we have the same restrictions of 10' max below grade?

Even if not, can't say I'm thrilled about having that many joints below our building above. Thanks for your help/thoughts!

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For determining the capacity of a water storage tank, is the tank capacity calculated by the max flow extension of a pump curve or by 140% rated capacity? Or could it even be 120% of the pump rated capacity?

Looking for guidance on how the pump size and water storage tank size would be directly related.

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I was recently cited by a surveyor for not having supervised control valves (isolation gate valves) on the jockey pump.

All other control valves are supervised for the riser and fire pump. I view the jockey pump as not critical or a necessary part of the fire pump and would not have an adverse effect if the jockey pump were out of service for any reason.

Is there a NFPA code reference that requires supervision on jockey pump gate valves?

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I am trying to understand how low suctions control valves in a fire pump work.

At what point would you need to have one? Could anyone help me understand that?

Thanks in advance. 

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I'm looking at a few projects that have fire pumps and above-ground cylindrical storage tanks for fire protection.

Some projects I have seen have recirculation after the fire pump discharge underground and back into the storage tank. Frustrated I can't find much on this in NFPA 22 or elsewhere.

Is this part of a means for freeze-protection, or to keep the water from getting stagnant, or for pump testing (in which case I guess it would have to branch off from the flow meter)?

Or is it likely engineer preference? Is it a military requirement?

Thanks in advance.

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I am doing some work on a combined fire-fighting/domestic pump house for a small community.

A couple things look odd to me.

1. They have a 12-inch flanged basket strainer after the pump discharge just before the mains. I was under the impression that any devices or fittings between pump discharge and need to be listed for fire protection use.
   
2. Instead of a jockey pump, they have three potable water pumps which run all the time pushing potable water to the mains. The primary fire pump automatically operates when the pressure drops to 4.5 bar and the backup pump at 2.3 bar.
   

There seem to be two deviations from NFPA standards here:

First, the jockey pump should be small , so that in case of fire it is the fire pump taking the load, and second, the starting sequence requires the jockey pump to start above the fire pump churn, the first fire pump a little lower and so on.

Is there any exception for such combined domestic/fire protection systems in the NFPA line of standards?

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What is the best procedure to use when testing a 3,500 gallon diesel fire pump that is equipped with a throttling/pressure governor installed on it?

My graph was well below the rated curve at 50% and 100%, but the governor seemed to disengage at 150% flow and my numbers exceeded the rated curve when we pushed this much water.

I did not attempt to change the controller settings or unplug the device (if that's even possible) to disengage the forced idle at 50% or 100% but insurance isn't "buying" that the pump didn't fail. These pumps aren't more than 5 years old and are ran on a tight schedule once a week (by the way).

Maintenance thinks it'll lead to faster wear and tear on the motor and I agree. All I could really do was state the facts and hope I don't have to go back out there and do the test again.

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