I'm working on a a high-end hotel which will have a vertical turbine fire pump above a water storage tank.

Can we waive a minimum pump submerge depth by installing an anti-vortex plate between the pump's bell and the strainer?

The fire pump is a 1,500 gpm vertical-turbine type, located directly above the water tank. The tank depth is 6'-3" from the overflow bottom down to the tank floor. The water tank area is 2,408 sqft. The selected pump recommends 51.63-inches as a minimum submerge depth. This is in addition to a 12-inch clearance between the bottom of the strainer and the tank floor. The water level to be maintained inside the tank then must be 63.63-inches (95,511 gallons).

The remaining active volume in the tank after extracting the required volume will be 112,582 - 95,511 = 17,071 gallons. This is not enough to run the pump set for the required time under NFPA 13 2019 (Table 19.3.2.1 and 19.3.3.1.2).

Can adding an anti-vortex plate between the pump's bell and the strainer waive this minimum submerge depth? If not, what might be a recommended solution for this?

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Hi, all! I came across this forum by accident at the perfect time. I am having a dilemma with the building department.

I am conducting an annual flow test on a 500 gpm (at 100 psi) fire pump from the test header off the pump discharge with the valve closed as to not disturb the system. I achieved 100% and 150% with no issues and the curve was almost identical to the pump's design curve.

The Department of Buildings is rejecting the test because the test was conducted from the discharge manifold. I was trying to avoid flowing from the roof because it's a very high end building and did not want to risk anything. Now, this system has been recently installed and the jockey pump panel is reading 100 psi on the system.

When I tested my pump, it pushed out 168 psi  on discharge and 48 psi on suction for a net of 120 psi (the pump is rated at 124 PSI for churn). I can conduct the test from the roof with no issue as long as the building feels comfortable with their storm drain's ability to handle the flow, but I am worried about over-pressurizing the system. 

Am I permitted by code to test off the header and not from the roof? 

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If a fire sprinkler systems is designed for "life safety" purposes, should not a primary and standby fire pump be provided? Why are standby pumps not required to improve reliability for these systems?

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We have a building with a double check backflow assembly on the suction side of a fire pump. Normally there is a minimum of 10 pipe diameters of vertical plane pipe just before the suction flange.

Is the double check backflow allowed within that distance?

Are there requirements for the backflow to have flanges vs. grooved connections?

A colleague said the control valve should be OS&Y rather than butterfly on the suction side only. Why would this be the case? I would assume the OS&Y would reduce turbulence better than a butterfly, but wouldn't the checks also cause turbulence?

Thanks in advance.

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A couple of questions about an electric vertical inline fire pump:

(1) Is it necessary to build a rated room around a fire pump that is located in a boiler room that is already 2-hour rated construction?

(2) Is it required to have a concrete base poured below a vertical fire pump if we can bolt the pipe flange stand to a concrete floor?

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Some fire pump assemblies have closed-test loops. When we circulate water through this closed test loop, why does the suction pressure not increase?

I'd be interested in understanding the physics of the situation a little better here.

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I'm putting together design-build requirements for a new single-story construction building. The flow test pressure is borderline in my opinion so I'll be calling for a fire pump.

When is a water storage tank required with a pump?

I don't think the system needs one, but I just want to be sure.

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Do you know of any specific guidelines for space around a fire pump skid to leave in a fire pump room?

I have always worked off the notion of "enough clearance to get around and work on a pump" but that is very subjective. So, I have a self-imposed 3-foot clearance around the edges of a skid. 

Is there anything more specific in generally adopted codes or standards?

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When/why would an eccentric reducer ever be installed on a fire pump's suction side with the flat side on bottom?

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I have a project where the fire pump room is located on a third floor level.

Are there any specific requirements regarding the location of a fire pump? Is this location acceptable?

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By code, does the check valve on the discharge side of a fire pump, or jockey pump, need to maintain any specific distance from the pump itself?

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Are there any drawbacks of testing a diesel-engine fire pump on a main header where other diesel pumps are connected to, instead of a test header?

This is happening in my plant because the test header is is large enough that it would require frequent throttling of test header discharge gate valves for each pump, which has started to wear out and not hold pressure.

Also, what is the minimum flow requirement for weekly diesel pump testing considering the test header doesn't hold? Do we need to run 0%, 100%, and 150% flow test each week?

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Can a split-case fire pump be used with a suction that is below negative 1.5 psi of pressure (below 1.0m)?

Would this be acceptable under NFPA 20?

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As part of acceptance testing for a fire pump we test the installed pump net pressures at various flows (churn, 100%, 150%) and compare that against the factory certified curve for that specific fire pump. 

For these tests, what is the pass/fail threshold?

What would fail this test, and how far off could the installed pump be to fail this test?

As I understand it, the installed fire pump cannot differ from the factory certified curve more than the error in the measurement equipment (the allowed error in gauges, typically 1% of the gauge reading). I'm not sure if that's the proper way to go about it, but was curious if there's a better pass/fail mark I should be looking for with these tests.

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​A fire pump's speed is altered from 1760 to 1800 rpm. What is the new head if the original was 120 ft?
a. 115 ft.
b. 123 ft.
c. 126 ft.
d. 128 ft.

Solution | Posted 10/21/20

I have a question on the difference between Fire Pumps vs. Sprinkler Booster pumps test header connections.

In NFPA 20 (2007 Edition) they speak of a test header connection to verify fire pump capacity via either a 3-way or 5-way connection depending on pump capacity. I have a test header with a flow meter installed and I am aware that test header connection is required for a "FIRE PUMPS".

My question .. does this also apply to " Sprinkler Booster Pumps"? They are also under NFPA 20 but little mention is made.

Should a test header be installed at all?

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In an existing building with no fire pump test header, is it permissible to use Standpipe 2-1/2" fire hose cabinet valves to conduct a flow test for smaller pumps?

I believe NFPA 20 (2019) 4.22.3.1.3 (2) indicates that this approach is acceptable, but I would like to confirm.

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The pressure gradient that causes a liquid to move through the intake line to the pump impeller is:
a. total static head
b. net positive suction head
c. net discharge head
d. rated head

Solution | Posted 09/30/20

A high-rise building is to use a pressurized tank (half air-half water) to supply automatic sprinkler systems. If hydraulic calculations determine that 55 psi is required to supply the sprinkler system, what tank pressure is required?
a. 55 psi
b. 95 psi
c. 125 psi
d. 140 psi

Solution | Posted 09/28/20

I have a job where there are two existing diesel fire pumps that serve an existing warehouse (2 million sq. ft +).

The building is surrounded by an existing 12" underground fire supply loop. The two diesel pumps serve the space.

According to the property manager the system operate as follows:
(1) Pressure is maintained at 160-175 psi.
(2) Below 160 psi the jockey pump turns on to maintain 160-175 psi.
(3) Fire Pump #1 turns on when pressure drops below 150 psi to maintain 175 PSI. (Fire Pump - Static: 165 PSI ; Residual: 134 PSI @ 2000 gpm).
(4) Fire Pump #2 turns on when pressure drops below 140 psi to maintain 175 PSI (Fire Pump - Static: 190 PSI; Residual: 174 PSI @ 2000 gpm).

The pumps are provided by a municipal supply and a back-up private lake dedicated for the fire service.

The pumps are in parallel, so you would add the flows. And to my knowledge the higher pressure would overtake the smaller pressure.

My question is, how do you determine how to calculate the system hydraulically?

If I only use fire pump #1 for water supply, it will not be an accurate representation on how the system operates. In this case it also is very difficult to get the system to work hydraulically off of one fire pump.

I appreciate any input!

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The static discharge head is equal to the sum of all of the following except:
a. total static head
b. discharge system losses
c. suction system losses
​d. net suction head

Solution | Posted 09/21/20

In an existing building utilizing a “booster pump” or unlisted fire pump for a standpipe or sprinkler system, is there a suggested annual flow test procedure?

I realize there is no manufacturer’s data (0%,100%,150% rated capacity) to compare the results against.

Should it be excluded from the annual flow test requirements, and just flowed during the 5 year roof top flow?

I would appreciate input as well as, what others in the industry are doing to address this fairly common scenario.

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I have a horizontal split-case fire pump, with suction taken from the header. The distance from the flange of the tee to the pump flange maintains the minimum 10-pipe-diameters as required by NFPA 20. 

However, is the 10-pipe-diameters measured from the flange of the gate valve (OS&Y vale) or from the flange of the tee?

I received a comment from a consultant that stated the 10-diameters is to be measured from the OS&Y gate valve flange.

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I’m working in the construction of 4-star hotel. The water storage tank is underground made from concrete and the pump room is located above the water tank. The designer specified the fire pumps to be vertical split-case type! In order to follow code, I proposed to install vertical turbine pumps instead of the specified vertical-split case.

The supervisor Engineer is insisting to follow the specification of the fire pump and pushing me to create an underground pump room in order to install the specified pump set.

Any recommendations to avoid this directive?

I have a bad flooding experiences with this this type of subgrade pump rooms.

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We have a fire pump room which is very constrained. 

NFPA 20 (Edition 2016), A.4.21.1.2 (2) For horizontal split-case fire pumps, there should be a distance of not less than 10 diameters of suction pipe for side connection (not recommended) to the fire pump suction flange.

The main pumps have a capacity of 3000 gpm (two are electrically-driven and two are diesel-driven) with two jockey pumps at 300 gpm capacity. All are in one room. Pumps suction and discharge pipe  size is 12" as per Table 4.27 (a).

In this scenario, what is the meaning of 10 diameters - is it 10 times of suction size diameter of pump (means 10x12= 120") or something else?

Why is this requirement only limited to suction and why not for discharge side as there is tapping for pressure monitoring? Any thought would be much appreciated.

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