Need Auto. Standpipes when Fire Pump Provided?

10/22/2025

I'm working with a not-so-good flow test on a project that will require a pump because of the flow test.

Where this is getting in the muck is the test flow rate being 712 gpm. The hydrant is about 565 feet from the entry and about 4 feet below finished floor elevation.

This is a 5-story, light hazard with 2 standpipes, so the standpipe demand is 750 gpm.

Flow test had 44 psi static and 34 psi residual with a 0.9 coefficient through the 2.5" outlet. As you know this is a 750 gpm system demand.

The person over me is adamant that we not separate the sprinkler and standpipe systems out - sprinklers and then standpipe - by code when it comes to fire pumps. Even though this is a low-rise building and all we are technically concerned with is an automatic sprinkler system, and if the responding FD has an engine/pumper, the manual standpipe is in their realm.

The argument is that they don't want a "partially automatic system" on any project; if a fire pump is to be provided for the project, they insist that the standpipe system connected to it must also be automatic.

Back to the 750 gpm thing. At 34 psi, we have 712 gpm, obviously. The thing here is putting a 111 psi, 750 gpm pump on. They're concerned with the NPSH of the pump and not the duty point or the 150% rated test goals.

(1) When a fire pump is provided to meet the needs of the sprinkler system, are the standpipes required to be automatic?

(2) Is there a requirement here for automatic standpipes that I'm missing? The local jurisdiction has no amendments that affect standpipe requirements different than the model IBC.

(3) Is an automatic standpipe here even achievable given the limits of the water supply, or are we causing more issues in testing down the road?

If it was local, the FMs have already told me that's close enough and we will make up any flow from our trucks. What am I missing here?

I understand clearly that at 20 psi the flow is 1,124 gpm. That's not what I'm trying to accomplish. I am attempting to make the combined system fully automatic per policy at 750 gpm and I'm told it's all good to go.

Help a man at wit's end out here.

TLDR: How would you approach manual vs. automatic standpipes when a fire pump is provided for a 5-story sprinkler system, but a 750 gpm pump could overtax the water supply?

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7 Comments

Dan Wilder link

10/22/2025 07:58:49 am

My approach would be an automatic sprinkler system with the pump as needed, interconnected standpipes but designed for Manual and using the local AHJ pumper truck capabilities for that water supply. That is a typical SOP for design of buildings with floors in the 30'-75' realm based on available water supply. Signage on the FDC will be key for the responding pumper truck and engineer.

1 - No, they are separate designs and the connection between the two is typically setup where the sprinkler system is automatic, the standpipe can be automatic or manual. There are some IFC provisions that require an Automatic standpipe and are clear - Assemblies >1000, Underground buildings and some others...these all state "Automatic"

2 - No, requirements for Automatic provided you are in compliance with the IFC (2021 ref.) 905.2 - 905.11. In your case, 905.3.1 (1) Four or more stories above grade plane, 905.3.1(2) Floor level of the highest story is located more than 30 feet above the lowest level of the fire department vehicle access and using the Exception (1) to allow Class 1 is the likely path. Nowhere is the term "Automatic" used in reference to a standpipe requirement (using the provided info).

3 - Most likely....I don't see the full 150% being achievable/ available at 20 PSI...take into account losses from pipe and fittings and you'll likely drop below that 20 PSI threshold and possible approach the 3PSI or lower. If the full 150% cannot be made, you can use the provision in NFPA 20 (2019) 14.2.6.3.4.1 for the acceptance, if the local AHJ allows.

Glenn Berger

10/22/2025 08:15:17 am

1) Standpipe System can be Manual Wet Class I type iaw NFPA 14. It does not matter that the building is provided with fire sprinkler system(s).

2) The code requirement is that standpipes are required. The exact system type needs to be developed based on locality issues.

3) Automatic standpipes can be achieved. May need water storage tank to be included in the design.

Anthony

10/22/2025 08:45:41 am

(1) No this is why you have an FDC let the pumper truck feed the manual system-- see the back of NFAP 14 it has design criteria when you cant get truck pump curves

(2) None that I'm seeing

(3) I'm worried you wont pas your flow test on commissioning you should be required to have a hydrant within 100 ft of the FDC unless AHJ allows otherwise. (can anyone else confirm?)

Casey Milhorn

10/22/2025 08:50:00 am

Dan and Glenn nailed it. The only thing I would add is to make sure the path from the FDC(s) to the hose valves are sized no smaller than 4", but should be sized larger if required by a manual standpipe calculation, using the responding fire departments fire pumper supply information. Remember to provide signage at the FDC that signifies a manual standpipe and the required pressure. IF the fire department can and will energize the system to more than 175 psi, make sure you take that into account for your materials used in the systems. It's not a bad strategy to keep your required static psi to 175 psi in your manual standpipe calcs, and then to signify that on your signage. This avoids the 175 issue and should reduce your exposure if the fire department supplied excess pressure and has a failure. BUT, if the fire department says they will pump to over 175 psi regardless of signage as their SOP, I would consider this.

Donnie

10/22/2025 11:28:23 am

Yes, manual standpipes are allowed where the building is fully sprinkled. The fire truck pumper can then satisfy the pressure needed at the top most remote outlet of 100psi. If you need more bpm, open another hose outlet to get 750 combined total flow. Should be easy.

Jerry Clark

10/22/2025 01:32:22 pm

For a 5-story light hazard building under the model IBC (without local amendments), standpipe systems are required but are allowed to be manual wet. NFPA 14 and IBC typically require automatic standpipes only for high-rise buildings over 75 feet or special conditions. Your building's standpipes do NOT need to be automatic simply because a fire pump is installed for sprinklers.

Since your local jurisdiction has no amendments altering standpipe rules, no hidden requirement forces the standpipes to be automatic if a fire pump is added for sprinklers. Manual wet standpipes supplemented by the fire department's pumpers are code-compliant and standard practice.

The available supply showing 34 psi residual at 712 gpm is marginal for a 750 gpm combined demand system with a fire pump rated at 111 psi. Attempting to make the standpipe system fully automatic under these conditions can lead to pump NPSH problems, test difficulties, and potential system operational issues.

Jack G

10/22/2025 05:42:13 pm

Both NFPA 14 and the IBC would allow a manual wet standpipe system here. Calculation would be from a hydrant to a pumper truck thru the fdc to the standpipe system usually calculated with the flow( here 750 gpm) at 150 psi. The standpipes shall be a minimum of 4 inch. Some times if the hydrant is too far away to calculate 100 psi with the 150 fire department pressure the AHJ will allow what the max pressure the fire department can provide.
A fire pump can also connect to the manual standpipe and sized only for the sprinkler system. ( Fire dept provides the standpipe flow and pressure)
In this case I would size the pump for 120% of the calculated sprinkler demand at a pressure that included the elevation loss plus the friction loss minus the water mains pressure at the flow.
I ve used a 400 gpm 90 psi pump for the sprinklers. I ve found this to be the best economical size.

Need Auto. Standpipes when Fire Pump Provided?

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