Does Local Requirement Constitute a Break Tank?

11/15/2023

We're designing an ESFR system for a warehouse where the city water can supply enough to meet our 2,000 gpm demand, but the local ordinances prevent a fire pump from being supplied directly by city water lines.

We are planning to install a 13,000 gallon bolted water tank for this reason.

NFPA 22 (2013 Edition) Section 4.1.4 allows tanks to be sized so that the store supply plus automatic fill can support demand over the required duration.

However, Section 4.1.5 requires break tanks to be sized for a 15-minute duration of 150% of the fire pumps rated capacity. 13,000 gallons is enough to supply our demand with the added city refill rate, but is not enough on its own for a 15-minute pump supply duration.

Does Section 4.1.5 apply to my situation?

I'm not using an actual break tank, but the bolted tank is being used in a break tank-like fashion.

Thanks in advance.

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5 Comments

Dan Wilder

11/15/2023 07:23:08 am

By definition, a Break Tank is a tank providing suction to a fire pump whose capacity is less that the fire protection demand (flow x duration) so if the tank isn't providing the full capacity, you'll need to comply with the other provisions.

Unless you can get the tank to be defined (and comply) with another section, you've described and will have to comply with the break tank requirements.

Jesse

11/15/2023 08:10:24 am

Agree with Dan, I think you'll need to comply with the local break-tank requirements

Steven H.

11/15/2023 08:58:44 am

Agreed with Dan and Jesse. Take a look at NFPA 22: Section 14.5.1 -- it looks like your tank is being used to meet one of the first two items listed.
I would encourage looking at downsizing the fire pump if possible -- for instance using a 1500gpm-rated pump if you have a 2000gpm demand. This way, you can decrease the size of your tank to something around 33,750 gallons minimum usable volume (1500gpm * 150% * 15min).

In addition to needing to meet the sizing requirement, you will probably need to meet the refilling requirements outlined in 14.5.3 (specifically you would fall into the 14.5.3.1 section since your tank is sized for less than 30-minute of the sprinkler demand):

--14.5.3.1 If the break tank capacity is less than the maximum
system demand for 30 minutes, the refill mechanism shall
meet the requirements in 14.5.3.1.1 through 14.5.3.1.5.

--14.5.3.1.1 Dual automatic refill lines, each capable of refilling the tank at a minimum rate of 150 percent of the fire pump(s) capacity, shall be installed.

--14.5.3.1.2 If available supplies do not permit refilling the tank at a minimum rate of 150 percent of the rated pump capacity, each refill line shall be capable of refilling the tank at a rate that meets or exceeds 110 percent of the maximum fire protection system design flow.

--14.5.3.1.3 A manual tank fill bypass designed for and capable of refilling the tank at a minimum rate of 150 percent of the fire pump(s) capacity shall be provided.

--14.5.3.1.4 If available supplies do not permit refilling the
tank at a minimum rate of 150 percent of the rated pump
capacity, the manual fill bypass shall be capable of refilling the
tank at a rate that meets or exceeds 110 percent of the maximum fire protection system design flow.

--14.5.3.1.5 A local visible and audible low liquid level signal shall be provided in the vicinity of the tank fill mechanism.

Adam

11/16/2023 06:51:24 am

As I understand it, a break tank is used to break the connection to the municipal water supply. It sounds like this is a true break tank.

Sean

12/31/2023 11:31:25 pm

not allowing direct supply does not make sense why?

Does Local Requirement Constitute a Break Tank?

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