Does Sprinkler System Affect Fire Flow Duration?

5/13/2021

I have an 83,000 sqft total (3-story) Type II-B new construction building under the International Fire Code.

Under IFC Table B105.1(2) I get a straight-table Fire Flow of 6,000 gpm at 4 hours.

However, IFC Table B105.2 allows buildings with automatic sprinkler systems to have a "Minimum Fire Flow" of "25% of the value in Table B105.1(2)", and a "Flow Duration" of the "Duration in Table B105.1(2) at the reduced flow rate".

With a sprinkler system, the Fire Flow becomes 1,500 gpm (= 6,000 gpm x 25%), that's pretty straight forward.

However, is the Flow Duration straight from the original reading of Table B105.1(2) (which is 4-hours) or is the duration taken from Table B105.1(2) at the new reduced Fire Flow Rate (lookup 1,500 gpm to get 2-hour duration)?

In short, is a 83,000 sqft Type II-B building Fire Flow actually 1,500 gpm at 4-hours, or 1,500 gpm at 2-hours?

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12 Comments

Alex Jenness

5/13/2021 09:04:35 am

Correct. 1500 GPM for 4 hours.

Darin Golden

5/13/2021 09:52:07 am

Table B105.2 is very clear that the required flow duration is at the reduced flow rate.
In the scenario provided the required fire flow and duration is 1500gpm for 2 hours.

Colin Lusher

5/13/2021 12:04:10 pm

I don't think that is correct. It says "Duration in table B105.1(2) at the reduced flow rate". I interpret this to mean the original duration at the reduced flow rate. The duration is 4-hours, the reduced flow rate is 1500 gpm.

SLL

5/13/2021 12:27:14 pm

I agree. If the Flow Duration was the original duration, it would say 'Valve in Table B105.1(2). However, it reads 'Duration in Table B105.1(2) at the reduced flow rate'.

James

5/13/2021 12:41:22 pm

I don't have access to IFC Handbook, but is there any commentary around it that might clarify this?

5/13/2021 02:30:00 pm

I looked at the commentary and it didn't provide any more clarification, but table B105.2 already says to use the duration in table B105.1(2).

5/13/2021 02:35:54 pm

Right, but the real question is which duration?

The duration that corresponds to the correct building size & construction type, or the duration that corresponds to the new, reduced flow rate. I don't know the answer to this one but I have traditionally interpreted this to mean the duration of Table B105.1(2) WITH a lowered flow rate (ie: 4-hours at 1,500 gpm).

5/14/2021 01:42:04 pm

If the table intended to require the original flow duration it would simply state “duration in Table” like it does for non-sprinklered building. Why would it state “duration in table at reduced rate” if it meant the same thing.

Furthermore reducing the flow by 75% is substantial in terms of available water and the subsequent hydrants from App C that are derived from the require flow in terms of numbers and spacing. Why would a reduction of 75% in flow and number of hydrants not include a reduction of flow duration. The duration is the least important factor in fire flow. So the idea that the ICC intends to protect the original duration while giving away the other two more important factors makes no sense.

Moderator

5/24/2021 07:45:09 am

Great discussion here - We're sending in a formal ICC interpretation request on this topic, and will post the feedback here when it comes in. Thanks for everyone's input on this!

5/27/2021 10:33:35 am

Here is the submitted request to the ICC staff for an informal code interpretation:

In the IFC, Table B105.2, is the Flow Duration for Fire Flow on a sprinklered building supposed to be taken from Table B105.1(2) by referencing the original construction type and building area, or by referencing a lower flow duration at the new reduced fire flow from having a sprinklered building?

Hypothetical example; an 83,000 sqft Type II-B Fire Flow straight from Table B105.1(2) is 6,000 gpm at 4-hours. With a sprinkler system under 903.3.1.1, Table B105.2 states the Minimum Fire Flow becomes 1,500 gpm (25% of 6,000 gpm). Is the Flow Duration still 4-hours, or is it 2-hours (looking up 1,500 gpm back on Table B105.1(2) to get a new corresponding Flow Duration).

5/27/2021 10:34:22 am

And here is the informal response from ICC staff:

The text in Table B105.2 is clear that the required duration for the fire-flow specified in Table B105.1(2) can be determined based on the calculated fire-flow after reductions are taken. The intent of Table B105.2 is to encourage sprinkler protection. Attached is an excerpt from the 2015 IFC Significant Changes manual addressing this issue.

As such, with respect to your specific example, the required fire-flow for a 83,000 sf building of Type IIB construction is 6,000 gpm with a duration of 4 hours based on Table B105.1(2). Since the building, in this case, is assumed to be fully sprinklered in accordance with NFPA 13 (Section 903.3.1.1), Table B105.2 allows the required fire-flow to be reduced to 1,500 gpm and a duration of 2 hours. Table B105.2 specifically states that when sprinklered, the duration specified in Table B105.1(2) should be based on the permitted reduced flow rate.

Greg Collier link

7/5/2022 11:45:29 am

Keep in mind not all AHJ's that use NFPA 13 or the IBC. Some do not use that appendix. as an Example NJ Fire Code requires an approved fire flow method by the Fire Official and references Land Use regulations in a Bulletin.

There are several methods to calculate fire flow, as noted in some other comments. ISO, Iowa, NFA, etc. local..

When the FO determines the Building and land use fire flow there may be additional flows other that just the building, as noted in the IBC appendix Note. You may not see the full 75% credit.

You may see only a 50% credit or additional flow requirements because of other outside demands that are exposures to the building.

I have found that when considering all factors and using the 50% credit as well as comparing any of the other fire flow methods the required flows are within 250 GPM. You may add 250-500 GPM for outside uses such as outside exposures or storage, even trucks at a loading dock. Outside uses may not be regulated.

Planners, designers and fire officials should consider fire fighting tactics, fire suppression systems, fire sprinklers and fire hose stream placement. You really have to think of the fire officer in the right front seat of the fire engine.

Does Sprinkler System Affect Fire Flow Duration?

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