PRV Options for Combined Sprinkler/Standpipe?

10/6/2025

Have 5 stories of parking with about 15 levels of residential floors above. For an enclosed, heated/conditioned garage we can use a wet system.

If we're using Extra Hazard Group 2 with high temp sprinklers or 11.2k sprinklers, which reduces our design area we know we need to account for "0.40 gpm/sqft x 2,000 sq.ft. = 800 gpm demand" at least.

A PRV floor control valve like a 2-1/2" Zurn ZW5004 tops out at 500 gpm per the data sheet.

Would it be possible to utilize two of these floor controls from different stairs and have an interconnected system on those levels?

Or would it be better to utilize to try and separate the garage level sprinkler system from the standpipe for those levels and use a master pressure reducing valve station on ground level to feed the 5 garage levels?

Would a redundant pressure reducing valve at a master pressure reducing valve station be necessary if the sprinkler feed is separated from the standpipe feed for those levels?

Or could I just use a grooved 6" pilot-operated PRV like a Cla-Val 90G-21 (listed for 1763 gpm) before a floor control on garage levels?

(a combined sprinkler/standpipe configuration)

Lots to this, appreciate the feedback in advance.

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6 Comments

Jack G

10/6/2025 09:02:40 am

Yes a small redundant prv is required in parallel to a main prv.
Reasons being
Prevents valve chattereduces premature wear of the main prv and the small one by managing low flows
Improves pressure control- the main prv is set for peak demand and struggles for low flow
Provides redundancy
Manages jockey pump operations-- manages the pressure increases from the jp, which maintains system pressure. This prevents the main prv from constantly recycling which can Cause component failure.
Set the small prv to a slightly higher pressure than the larger prv.
During low demand, the small orv with the higher pressure, will activate first to handle the low flow.
As demand diminishes, the reverse happens, with the smaller prv closing last to maintain control during the lowest flow periods.
Size the smaller prv to about 20% of the larger one. ( or 1/3, 2/3 approach)

The settings must be staggered so that the valves do not fight each other.

Todd E Wyatt

10/6/2025 11:07:57 am

I recommend you first verify (from the Design Professional … Architect) the adopted scoping Code (IBC-2024?) to determine the requirements for the automatic sprinkler system (ASPS) as well as the standpipes systems (SS).

The Occupancy Classifications (OC) will be Group S-2 Low-Hazard Storage (parking garage) and Group R-2 Residential (residential) with other possible OCs (Group A Assembly, Group B Business, Group M Mercantile, Group S-1 Medium-Hazard Storage, etc.).

Based on your description, the Project sounds like it is a High-Rise Building (HRB) using one of the Section 510 Special Provisions.

Interconnection of Standpipe Hose Connections (SHC) is listed in IBC-2024 Chapter 9 Fire Protection and Life Safety Systems 905.4 Location of Class I Standpipe Hose Connections 905.4.2 Interconnection and 905.6 Location of Class III Standpipe Hose Connections 905.6.2 Interconnection which both reference NFPA 14 (see REFERENCES below).

NFPA 14 – 2024 Chapter 9 Installation Requirements 9.4 Interconnection of Standpipes includes the requirements for “Interconnection of Standpipes”.

10/6/2025 11:08:37 am

REFERENCES
IBC-2024

Chapter 4 Special Detailed Requirements Based on Occupancy and Use
Section 403 High-Rise Buildings
403.3 Automatic Sprinkler System
Buildings and structures shall be equipped throughout with an automatic sprinkler system in accordance with Section 903.3.1.1 and a secondary water supply where required by Section 403.3.3.
403.3.1 Number of Sprinkler Risers and System Design
The number of sprinkler risers and system design shall comply with Section 403.3.1.1 or 403.3.1.2, based on building height.
403.3.1.1 Buildings 420 Feet or Less in Height
In buildings 420 feet (128 m) or less in height, sprinkler systems shall be supplied by a single standpipe or sprinkler express riser within each vertical water supply zone.
403.3.1.2 Buildings More Than 420 Feet in Height
In buildings more than 420 feet (128 m) in height, not fewer than two standpipes or sprinkler express risers shall supply automatic sprinkler systems within each vertical water supply zone. Each standpipe or sprinkler express riser shall supply automatic sprinkler systems on alternating floors within the vertical water supply zone such that two adjacent floors are not supplied from the same riser.
403.3.1.3 Riser Location
Standpipes or sprinkler express risers shall be placed in interior exit stairways and ramps that are remotely located in accordance with Section 1007.1.
403.3.2 Water Supply to Required Fire Pumps
403.3.3 Secondary Water Supply
403.3.4 Fire Pump Room
403.4 Emergency Systems
403.4.3 Standpipe System
A high-rise building shall be equipped with a standpipe system as required by Section 905.3.

Chapter 5 General Building Heights and Areas
Section 510 Special Provisions
510.2 Horizontal Building Separation Allowance
510.4 Parking Beneath Group R

Chapter 9 Fire Protection and Life Safety Systems
Section 905 Standpipe Systems
905.3 Required Installations
Standpipe systems shall be installed where required by Sections 905.3.1 through 905.3.7. Standpipe systems are allowed to be combined with automatic sprinkler systems.
905.3.1 Height
Class III standpipe systems shall be installed throughout buildings where any of the following conditions exist:
1. Four or more stories are above or below grade plane.
2. The floor level of the highest story is located more than 30 feet (9144 mm) above the lowest level of fire department vehicle access.
3. The floor level of the lowest story is located more than 30 feet (9144 mm) below the highest level of fire department vehicle access.

905.4 Location of Class I Standpipe Hose Connections
Class I standpipe hose connections shall be provided in all of the following locations:
1. In every required interior exit stairway or exterior exit stairway, a hose connection shall be provided for each story above and below grade plane. Hose connections shall be located at the main floor landing unless otherwise approved by the fire code official.
Exception: A single hose connection shall be permitted to be installed in the open corridor or open breezeway between open stairs that are not greater than 75 feet (22 860 mm) apart.
905.4.1 Protection
905.4.2 Interconnection
In buildings where more than one standpipe is provided, the standpipes shall be interconnected in accordance with NFPA 14.

905.6 Location of Class III Standpipe Hose Connections
Class III standpipe systems shall have hose connections located as required for Class I standpipes in Section 905.4 and shall have Class II hose connections as required in Section 905.5.
905.6.1 Protection
905.6.2 Interconnection
In buildings where more than one Class III standpipe is provided, the standpipes shall be interconnected in accordance with NFPA 14.

NFPA 14 – 2024
Chapter 9 Installation Requirements
9.4* Interconnection of Standpipes.
A.9.4
Fire department connections feeding interconnected standpipes, including combined systems, should be arranged to supply all interconnected standpipes in a building or section of a building. Interconnection should occur as close to the source of supply(ies) as possible.
Standpipe systems in separate buildings or structures fed by the same water supply are not required to be interconnected. For example, a building might have an automatic-wet standpipe system while an adjacent parking garage has an automatic-dry standpipe system fed by the same fire pump and water main. These two standpipe systems are not required to be interconnected since they protect different structures.
9.4.1
Where two or more standpipes are installed in the same building or section of building, they shall be interconnected.
9.4.1.1
Standpipes shall be permitted to not be interconnected where acceptable to the AHJ.
9.4.2
Where standpipes are supplied by tanks located at the top of the building or zone, the standpipes shall be interconnected at the top.
9.4.3
Dry standpipes shall have only a single level of interconnection.

Brett

10/6/2025 12:55:28 pm

In order of the statements and questions:

- Just curious, why EH2? Does the local AHJ make you do this for EVs and EV chargers? We have an AHJ who makes us do this.

- Two interconnected floor controls is done all the time in very tall buildings but it's still an ITM accident waiting to happen. Flooding a parking garage obviously isn't as big of a deal as flooding the units above, but it's a risk I wouldn't be willing to take just to save money on a PRV.

- We have done the master reducing valve for a sprinkler riser that feeds lower levels of a not-so-high high rise and found success with it.

- If the PRV only serves a sprinkler riser then you do not need a second redundant PRV in series. That's only required for standpipes.

- You could do a PRV at each floor, yes. The master PRV versus one at each floor just comes down to price. Price out five PRVs versus one PRV with an additional five-story riser and see what that comes out to.

Mark

10/6/2025 03:05:16 pm

Agreed

Master PRV for standpipe only with a seprate complment of pipe for not so High High rise

No need for anything else on a 5 story building

L Scott

10/8/2025 11:34:34 am

Responding to mostly Brett's thoughts here:

- (1) Local AHJ requires, for example some Florida bigger city local municipalities require EXG2 and additional FHVs within 100ft. I think California might have some similar requirements.

- (2) I had the same thought process regarding accident waiting to happen. But didn't even know if it was even a viable option to meet the gpm.

- (3, 4, 5) Sounds like separating the garage floors standpipe supply and a sprinkler supply with a PRV on the sprinkler supply might be the most cost efficient method will have to confirm with what that does to pipe sizes on the upper garage levels. Ultimately it looks like the garage stairs will align with the residential layout and continue through to the top of the highrise, so on garage levels the supply would act as just the standpipe and then continue to residential levels above it would be standpipe & sprinkler. And then on garage levels a separate PRV controlled sprinkler-only supply for those garage levels.

I think I need to look into a low-flow PRV based on Jack G's comments.

PRV Options for Combined Sprinkler/Standpipe?

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