Section 903.3.5.2 (IBC 2012)/Section 403.3.3 (IBC 2015) requires and automatic secondary water supply. I am an FPE and I work in a jurisdiction (Hawaii) that has never required this secondary water supply due to local code amendments to IBC. Recent code revisions now require this secondary supply, and I now have my first project subject to this requirement. I'm planning to meet this requirement as as follows;
Am I on the right track here? Is this primary/secondary supply arrangement viable? Does anyone foresee any code or other issues that may be a problem with this arrangement? Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe
14 Comments
Jesse
11/29/2021 08:30:03 am
We see some AJs in Texas that have various iterations of this. Its common to use the break tank as this secondary source.
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Colin Lusher, FPE
12/2/2021 05:22:51 pm
Standpipe system demand is per NFPA 14, which is 750 gpm with 100 psi at the most remote hose connection (roof); this translates to 750 gpm @ 250 psi for the fire pump on floor 1 to meet the requirements on the top floor (17th).
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Michael Lantaigne
11/29/2021 09:07:51 am
My experience with this situation is where a secondary water supply is required for the sprinkler system in a high rise building with a seismic design category of C, D, E or F (2015 IBC 403.3.3). I don't believe the tank necessarily needs to be sized to provide the standpipe demand since the code specifically mentions the hydraulically calculated sprinkler demand including hose streams. It is worth noting that depending on the hazard in the building, the sprinkler demand plus hose allowance could exceed the standpipe demand.
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Colin Lusher, FPE
12/2/2021 04:30:03 pm
Yes, this requirement is for the seismic design category of C, D, E or F (2015 IBC 403.3.3).
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COLIN LUSHER, FPE
12/2/2021 05:28:50 pm
"however you would not be able to reduce the tank size based on the refill rate since it would not be a full secondary supply in the event that the city supply was damaged."
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Brad K
11/30/2021 03:52:01 pm
I feel like you are using one tank as both storage and break tank.
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Colin Lusher, FPE
12/2/2021 04:34:58 pm
It is a storage tank when the city water supply is NOT working.
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Alex
12/1/2021 10:26:50 am
Hi,
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Colin Lusher, FPE
12/2/2021 04:39:00 pm
The IBC code specifically states that a second fire pump is NOT required if you can meet the system demand with a single pump.
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sean
12/31/2021 06:40:31 pm
why are you sizing the secondary for sprinkler and standpipe, nothing in the code that i know of states you need both just the greater
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Colin Lusher, FPE
1/10/2022 11:23:25 am
I'm not. The "Secondary" supply is only required to meet the demand of the fire sprinkler system, NOT the standpipe system. The section of IBC that specifies the secondary supply only applies to fire sprinkler systems, not standpipes, so it's not a case of meeting the "highest demand system" in this case. I confirmed this with NFSA via informal code interpretation. I only stated that the pump itself will be sized to supply the highest demand system (standpipe).
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Jimmie
6/9/2022 06:33:35 am
I am in agreement here. Although, some interpret "including hose stream requirement" to mean the standpipe demand, I don't think this is the case. It is referring to the 1-1/2 inch hose connections as per 20.14 of NFPA 13 (2022), which short of storage commodities you would be unlikely to have in a building. Having said that, we have had AHJs still require 100 gpm for the hose streams, but still better than 250 gpm per standpipe.
Travis
7/25/2023 09:52:43 am
What is the code regarding a high rise building that is in a seismic zone but only has a cistern water tank for the primary water? There is no water main available for connection. Would a secondary water tank still be required? It seems that the second water tank would not really be a secondary water source but in essence a duplicate of what is already installed.
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COLIN LUSHER, FPE
7/25/2023 10:37:36 am
Yes, a second tank would be required.The second tank would be a redundant supply, therefore increasing reliability of the system. Redundancy is a common approach to increase reliability and availability of a system, which is exactly the purpose of this code requirement.
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