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

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!

​​​​​​​​​​​​​​​​Submitted anonymously and posted for discussion. Discuss This | Submit Your Question | Subscribe

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.

​​​​​​​​​​​​​​​​Submitted anonymously and posted for discussion. Discuss This | Submit Your Question | Subscribe

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.

​​​​​​​​​​​​Submitted anonymously and posted for discussion. Discuss This | Submit Your Question | Subscribe

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.

​​​​​​Submitted anonymously and posted for discussion. Discuss This | Submit Your Question | Subscribe

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.

Submitted anonymously and posted for discussion. Discuss This | Submit Your Question | Subscribe

Is there something where I can input fire pump test results and create a fire pump curve that I can print off and include with fire pump testing results? Possibly something I can input our company name on as well? Thanks in advance.

​​​​​​​Posted anonymously for discussion. Discuss This | Submit Your Question | Subscribe

In regards to a dry-pipe system with a fire pump on the supply; is a jockey pump required on the wet portion between the pump and the dry-pipe valves?

I have to assume the answer is yes, since pressure needs to be maintained in this line if leaks develop over time. Please confirm/advise. Thanks in advance!

​​​​​​​​​​​​​​​Posted anonymously for discussion. Discuss This | Submit Your Question | Subscribe

I am dealing with an extremely small fire pump room with limited wall space for the controllers. The only available space to route some of the wet main piping will be directly above the fire pump and jockey pump controllers.

Do the requirements from NFPA 70 concerning dedicated electrical space apply to fire pump controllers and the fire pump piping?

​​​​​​​​​​​​Posted anonymously for discussion. Discuss This | Submit Your Question | Subscribe

My employer owns several properties in with 2 fire pumps that are discharging to the same loop. The pumps were there when we bought the buildings.  In most cases there is one electric and one diesel, but in other cases there are two diesel fire pumps.

The power purveyor is not considered unreliable by any criteria.

Is there anything you can think of that would prohibit me from decommissioning a redundant pump for the purpose of saving on maintenance costs?

Each pump is 2000 gpm and the greatest demand on the loop is less than 3,000 gpm. The pumps are provided in parallel. 

​​​​​​​​Posted anonymously for discussion. Discuss This | Submit Your Question | Subscribe

A question for the pump experts on the forum; the line of horizontal split-case fire pumps I'm familiar with generally come as 1770 RPM or 3560 RPM.

What is the benefit to using one versus the other? Do contractors generally have a preference? Is cost, sounds, wear-and-tear impacted by the RPM selection? Thanks in advance.

​​​​​​​​Posted anonymously for discussion. Discuss This | Submit Your Question | Subscribe

Big picture question here - I am working on an airport project. We have a Passenger Terminal Building and Aircraft Stands adjacent to the building.

I need to provide sprinkler protection with fire hose cabinets in the Passenger Terminal Building (1,000 gpm at 8 bar / 100 psi), AND fire hydrants to resupply the aircraft rescue and firefighting trucks (1,500 gpm at 6 bar / 87 psi).

Do both of these demands need to be considered together to size the fire pump (both flows combined)? 

We are considering one duty pump and one standby pump. Thanks in advance.

​​​​​​​​Posted anonymously for discussion. Discuss This | Submit Your Question | Subscribe

Split case pump - flow meter installation question:

As indicated in NFPA 20, the distance from the flowmeter to either isolation valve should be as recommended by the meter manufacturer.

​Based on your own experience, do fittings (elbows or bends) need to be included in this distance calculation?

For example - should the distance recommendation length of 10-diameters be calculated from the last fitting or is the fitting ignored and only calculated from the isolation valve? Thank you.

​​​Posted anonymously for discussion. Discuss This | Submit Your Question | Subscribe

NFPA 20, 4.12.6 "Ventilation. Provision shall be made for ventilation of a pump room or pump house."

DIESEL FIRE PUMPS - These rooms require a lot more air for combustion air and heat removal. This is usually done in generator and boiler rooms with separate fan-forced intake air and exhaust ducts to the outside. In the case of a fire pump, fireproofing these ducts through the building offer additional "protection" under NFPA 20, 4.12.1 in the event of a fire. Diesel data sheets show the amount of CFM required for the various engines. In addition, the extra distance for the exhaust pipe lengths to the outside needs to be considered. Some of the engine manufacturers have calculators on their websites for VENTILATION, COOLING LOOP and EXHAUST PIPING.

PUMP ROOM TEMPERATURE LIMITS - Most microprocessor controllers are limited to 120 deg. F. A small non-vented pump room, especially on a west wall, could easily exceed that with a motor running under load on a hot 100+ degree day.

My question? This site/facility does not have an emergency backup generator. Do we need a backup generator to power the exhaust fan and/or the unit heater?

In the event of power loss during winter… a room temp sensor would send supervisory alarm company for an owner response.

Also, please confirm the Jockey pump does not require backup power.

​Posted anonymously for discussion. Discuss This | Submit Your Question | Subscribe

When testing a fire pump from the roof is there a calculation that is necessary to ensure that the flow test is accurate (given pipe sizes, elevation increase, etc)?

NFPA 25, 2014 handbook states that flowing from the roof in the explanatory material is somewhat acceptable (NFPA 25, 2014: 8.3.3.1.3). However, NFPA 20, 2013 A.4.20.3.4(2) has a sample hydraulic calculation sheet for sizing the test header when not using the table which appears to take into account items like friction loss, elevation, etc.

​​​​Posted anonymously for discussion. Discuss This | Submit Your Question | Subscribe

We have a project which is on a steep slope (the bottom of the site is about 120 feet lower than the top of the site). If we attach a fire main to the bottom of the site, the fire pump we have won't have much issue with keeping the city pressure at a 20 psi minimum or above.

If we attach to the water grid at with the fire service main at the top elevation of the site, we will probably need a suction control valve in order to keep the city pressure at 20 psi at the top elevation since the available water supply is so low.

My question is - if we pull pressure on a city's system at the low elevation, do we have to chart and consider the rest of the water supply network?

There's a chance if we pull the water supply down to 20 psi at the lower elevation that the system at the higher elevations would be well below the 20 psi due to elevation pressure loss. Thanks for your input!

​​​​Posted anonymously for discussion. Discuss This | Submit Your Question | Subscribe

Is there a complete list of points I need to monitor with fire alarm for a diesel driven fire pump?

I can't seem to find a comprehensive/definitive list in NFPA 20 or 72, but I would imagine at least one or more of the following would need to be monitored by code: fire pump running, primary sensor failure, low fuel level, main disconnect in "off" position, main disconnect in "manual" position, low pump room temperature, flowmeter left on, loss of AC power supply, loss of battery (load side of DC overcurrent), over-speed, and engine trouble (low oil, over temp, other?).

​​​​Posted anonymously for discussion. Discuss This | Submit Your Question | Subscribe

I have a fire pump rated at 100 psi at 1000 GPM. The curve for the pump is starts at 125 psi and goes to 0 GPM. I know 140% is the 125 PSI. On my hydraulic calculations should I use the 140% pump curve or should I use the 100% Pump curve? Where in NFPA 13/20 can I find this guidance?

​Posted anonymously for discussion. Discuss This | Submit Your Question | Subscribe

NFPA 20 permits the demand for a suppression system to be between 90% and 140% of a fire pump's rated capacity (NFPA 20-2019 4.10.1 and Annex A.4.10.1). The pressure demand must always be less than the pressure supplied by the pump's performance curve along this range.

Does this concept apply to standpipes? For instance, could a 750 gpm pump provide 1,000 gpm demand for standpipes since it would be running at 133% of its rated flow?

If it can be done, is it good practice?

​​Posted anonymously for discussion. Discuss This | Submit Your Question | Subscribe

Without the context of a specific project or problem, when would you recommend creating a separate, detached fire pump house versus a fire pump room inside a building?

Is is purely a risk perspective? Do you recommend fire pump houses only when a pump is feeding multiple buildings, or a campus?

I've only had a few projects that used a fire pump house, and it has generally been in retrofit situations or when the pump is next to a water storage tank. In either case the pump house overall cost more than it would have should the fire pump room been within the building (even despite the simple construction of the pump house). Just curious on getting another perspective.

​Posted anonymously for discussion. Discuss This | Submit Your Question | Subscribe