How do I properly perform hydraulic calculations for a sprinkler system with two water sources?

The system we have is supplied by two independent street mains. Each service has a slightly different static and residual pressure. The calculations need to show both supplies. Thanks in advance.

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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'm an AHJ and I know many plan reviewers and inspectors in my area are new to the trade. 

Does anyone have recommendation(s) for good plan review checklists or tools for plan review that would be helpful to rookie and intermediate-level plan reviewers?

Thanks in advance.

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What is the average life expectancy of a wet and dry fire sprinkler system?

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Fire sprinkler system design has been based upon all of the following except:
a. Empirical flow and pressure loss calculations
b. Application of experienced judgement and reasoning
c. Mathematical suppression modeling
d. Evolutionary changes based on fire loss

Solution | Posted 09/23/20

NFPA 22, 2018 Edition regarding filling requirement and duration - 

Section 4.2.1.4. states "The water supply shall be capable of filling the minimum required fire protection volume within the tank in a maximum of 8 hours" and at the same time Section 14.4.3 states "The tank shall be kept filled, and the water level shall never be more than 4 in. (102 mm) below the designated fire service level."

If I understand correctly, as soon as the water goes below 4-inches from the normal filled level in the tank (HHL), the makeup water supply should be starting to replenish and the pipe sizes should be provided in such a way that the tank can be filled within 8-hours.

In a fire, as the water is going down, the tank will always start full.

What is the case where the tank would be emptied out (except maintenance) and need to be refilled within 8-hours?

What if we store water in two tanks to allow maintenance - would we not need to meet this 8-hour requirement?

I'm unsure of how these two requirements work together. Appreciate any feedback.

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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

We have scenario where we are using foam system under NFPA 11 for a floating roof tank with Crude Oil.

Based on our previous calculation for a prior tank the fire water demand is 1,926 gpm so we have existing 2,000 gpm pump to be able to supply the required flow. But an additional Crude Oil tank has been added and we have run our new hydraulic calculations and we come up with 4,496 gpm new flow requirement.

Is there a way we can still use the existing fire pump?

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We have an outdoor wooden canopy overhanging over a building entrance with the following dimensions: 45'-6" x 13'-0". The canopy has an existing wet pipe sprinkler system utilizing water/glycol mix. The building is in an area where winter temperatures can go below 0 deg F (-18 deg C).

Given the new NFPA requirement of reduced glycol mix ratio and hence the existing sprinkler system is no longer compliant with NFPA and requires to be replaced.

My question is, is it feasible and compliant to have the wooden canopy treated with fire retardant NFPA 703 approved coating/painting and hence the canopy can be considered non-combustible or at least limited-combustible eliminating the requirement to install a sprinkler system under NFPA 13 section 9.2.3?

I appreciate your feedback. Thanks

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Working with a 10,500 square foot building that is primarily a wood shop (as the AHJ, fire official). In this building they basically saw cut raw lumber on a large gasoline powered (vented) saw mill inside of the building (this is an issue I question as well). This is a two-part question, at the least!

The occupants claim they are a E occupancy (based on the 2012 IBC/IFC) and that they fall under the 12,000 square feet for automatic fire sprinkler requirements in chapter 9.

I look at this as a woodworking facility over 2,500 square feet per 903.2.4.1, that would require automatic fire sprinklers.

The organization is not a school, but rather consider themselves as a vocational school that serves students working on their G.E.D. along with troubled students needing extra guidance, and they pay these students. They teach life/work skills and help with job placement.

I feel this would either fall under a B-Occupancy for training and skill development not within a school or academic program, or an F-1.

Thoughts on this part?

Next, even if we would call this an E-Occupancy, would sprinklers be required since it is under the 12,000 square feet? I would think yes because of section 903.2.4.1, however the organization says no because they believe they are an E.

​I know where I am leaning on this issue, but would welcome any other input. ​I am all about helping this organization out, but also need to take safety and property preservation into account. This place keeps me up at night with all of the students and hazards present.

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What is the greatest allowed spacing among all pipe sizes between hangers for CPVC pipe in fire sprinkler systems?
a. 6'-0"
b. 9'-0"
c. 10'-0"
d. 12'-0"

Solution | Posted 09/16/20

A class III commodity is encapsulated and stored on shelves within a large walk-in cooler. A dry system is being designed to serve this hazard. If the storage is anticipated to be 13 ft. in height with a 17 ft. ceiling, determine the required design density with the smallest remote area for high temperature sprinkler protection using the Control Mode Density/Area approach.
a. 0.14 gpm/sqft / 2,000 sqft
b. 0.14 gpm/sqft / 2,600 sqft
c. 0.15 gpm/sqft / 2,600 sqft
d. 0.18 gpm/sqft / 2,600 sqft

Solution | Posted 09/15/20

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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In an NFPA 13R system does the FDC check valve need to be accessible?

In 13 it states it is required, but I can't find it in NFPA 13R. Section 6.11.4 talks about ball drip for check valve, but I do not see anything on accessible. I’m sure I’m missing some code path that references 13 possibly? Thanks.

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We have a bowling alley that has bowling lanes constructed of wood, with supporting solid-wood members underneath. The bottom of the solid-wood support members are about 1-ft above the top of any other obstructions at the bottom of this concealed space, leaving a total height of roughly 2-ft below the lanes. This whole bowling alley (30+ lanes) is being retrofitted with sprinklers.

Are sprinklers usually provided underneath the lanes for areas like this? 

If so, how do we address inspection and draining from these areas below the floor level?

Thanks in advance.

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An warehouse facility is seeking to store cartoned Level 3 aerosol products on pallets. If the storage height is 10 feet in height with a 23 foot ceiling, what minimum k-factor must be provided for the ceiling level sprinklers protecting this area?
a. K-8.0
b. K-11.2
c. K-14.0
d. K-16.8

Solution | Posted 09/08/20

Is there a standard spacing for private fire hydrants?

No applicable code for this project, but looking for guidance in what would be common under NFPA 24, NFPA 1 / 101, and/or the IBC. Thanks in advance.

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A building owner has an existing mixed-use building which has approximately 6,000 sqft of storage space (S-1 Occupancy) and offices (larger than 6,000 sqft). The offices and storage appear to have a rated separation (steel studs, 2x gypsum on at least one side of the wall) in-between them.

The owner is looking to store new product in the warehouse, but would like for it to be sprinkler protected. This building, if new, would be under the 2015 International Building Code. 

As the building currently stands, it is a code-compliant mixed-use separated, non-sprinklered occupancy. 

Can the owner voluntarily provide a sprinkler system above code, but only for the warehouse portion?

If so, does anything with the fire barrier between the warehouse and office need to change?

As this is only a voluntary improvement to the property and life safety systems, I could see it being an alternative design method and seek approval from the AHJ under IBC Section 104.11 as a partially-protected building - I just wasn't sure if it even needed to come to that. Would be interested in other opinions, thank you in advance!

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I have a residential sprinkler calculation out of NFPA 13R 2016.

Do you need to calculate a minimum of 4 residential sprinklers within the dwelling unit?

I have a two-bedroom apartment unit and my most demanding area would be the two that are in the bedrooms and the two that are in the kitchen/living area.

Can I consider the kitchen/living area a compartment separate from the bedrooms and calculate only these two sprinklers?

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Would it be permitted by code to place a pre-action valve on top of a roof of a two-story building?

It would be protected from mechanical damage, and there's no regular man movement at the roof. The roof area is warm, but there would be no covering as it currently stands. I'm looking for code requirements pertaining to this situation that would allow or disallow such an arrangement.

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​Which of the following types of pipe would require the most hangers for the same length of 1-1/2" pipe?
a. CPVC
b. Copper Tube
c. Steel other than Threaded Lightwall
d. Threaded Lightwall Steel

Solution | Posted 09/01/20

What is the residual pressure and flow require for both public and private fire hydrants?

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A fire department connection may be installed by any of the following arrangements except:
a. Between the supply control valve and the system control valves for multiple sprinkler systems
b. Attached to underground system piping, between the supply control valve (at the main tap) and the system control valves (inside the building)
c. Attached to main pipe on a system (on the system side of the system control valve) for a single wet system
d. Attached to the main service between the utility tap and the entry into a fire pump room

Solution | Posted 08/31/20

What length of 6-inch Schedule 40 black steel pipe would provide the same friction loss as 24 feet of 4-inch schedule 10 black steel pipe if both are serving a wet sprinkler system at the same flow rate?
a. 4 ft
b. 34 ft
c. 135 ft
d. 173 ft

Solution | Posted 08/28/20