Water Supply · Definition
How Current Must a Flow Test Be, and Who Can Perform One?
Reviewed by a licensed Professional Engineer · NY, NJ, PA, MD, DE · Last reviewed · Code basis: NFPA 13 (2022) 4.5.1.1; NFPA 13 (2019) Ch 4; NFPA 13 (2025) Ch 4; NFPA 13 (2016) Ch 23 via NYC 2022 Building Code Appendix Q; NFPA 291 (2022) Ch 4; NFPA 25 (2023) Ch 13
General guidance, not a code determination for any project. Confirm the adopted code and local amendments with the authority having jurisdiction.
A current flow test, for sprinkler design purposes, is a water supply test run no more than 12 months before the working plans are submitted, unless the authority having jurisdiction (AHJ) approves an older one. The rule sits in Section 4.5.1.1 of the 2022 edition of NFPA 13, the National Fire Protection Association standard for sprinkler installation. The test itself is run by the water purveyor, or by a contractor the purveyor permits on its mains, and the reviewing AHJ decides whether the result is recent enough to design on.
The 12-month limit is short on purpose. Water mains age, pressure zones get re-valved, pumps are reset and demand grows, so a reading taken 3 years ago can overstate what the main will deliver on the day the sprinklers open. This article defines what “current” means, what a usable test record contains, which NFPA 13 edition carries the rule in each state DGA works in, who is allowed to run the test, and how a flow test differs from the letters and tests it is often confused with.
At a Glance: Flow Test Currency
- Definition: a hydrant flow test is current when it was run within 12 months before the sprinkler working plans are submitted for review, or when the AHJ has approved an older test.
- Governing code and section: NFPA 13 (2022) Section 4.5.1.1, as referenced by the 2024 International Building Code (IBC) in New York State and New Jersey. Pennsylvania and Maryland county permits use NFPA 13 (2019) Chapter 4; Delaware uses NFPA 13 (2025) Chapter 4; New York City uses NFPA 13 (2016) Chapter 23, as modified by Appendix Q of the 2022 Building Code.
- Who performs it or who it applies to: the water purveyor runs or permits the test on public mains; the owner’s contractor runs it on private mains; the sprinkler designer relies on it; the AHJ accepts or rejects it.
- When it’s required: before working plans are submitted, again if the project stalls past 12 months, and whenever the purveyor changes the system that feeds the site.
- Typical output: a one-page test record with date, hydrant locations, static and residual pressures, pitot reading and flow, and the name of the party that ran the test.
- Often confused with: a purveyor availability or will-serve letter, a fire pump acceptance flow test, and the NFPA 25 main drain test. None of the three measures the main’s capacity at the connection.
What the 12-Month Rule Says
NFPA 13 (2022) Section 4.5.1.1 requires that the water supply flow test used for the hydraulic design be conducted no more than 12 months before the working plans are submitted, unless the AHJ approves otherwise. The clock runs from the test date to the submittal date, not to the permit date or the installation date. A test that is 11 months old at submittal and 18 months old at acceptance is still a current test under the rule.
“Working plans” are the sealed sprinkler shop drawings and hydraulic calculations that the installing contractor or engineer submits for approval; NFPA 13 (2022) Chapter 28 lists what they carry, including the water supply information. DGA’s article on what sprinkler shop drawings contain describes that set. A preliminary design or a feasibility study can be built on older data, but the plan examiner reads the 12 months from the working plan submittal.
The exception is the AHJ-approval clause. A reviewer can accept an older test when the purveyor confirms that nothing in the system has changed, or when a newer test is not practical, for example a winter submittal in a district that does not flow hydrants below freezing. That acceptance is the AHJ’s decision, not the designer’s, and it should be in writing before the calculations are run on the older numbers.
What a Current Flow Test Record Includes
Age is only one of the things a reviewer checks. A test that is 2 months old but missing the hydrant elevations, the main size or the name of the party that ran it is a current test that cannot be used. The record should carry the items in the table; NFPA 291 (2022) Chapter 4 describes the procedure and what is recorded, and the hydraulic calculations in the working plans repeat the key numbers.
| Item | What the record shows | Why the reviewer needs it |
|---|---|---|
| Date and time of day | Calendar date and clock time of the readings | Starts the 12-month clock and shows whether the test caught peak demand (morning in a residential zone, midday in an industrial one) |
| Static pressure | Pressure at the residual hydrant with no hydrants flowing, in psi | The top of the supply curve |
| Residual pressure | Pressure at the same hydrant while the flow hydrant is open, in psi | The second point that fixes the slope of the supply curve |
| Pitot reading and flow | Pitot pressure at each flowing outlet, outlet size, coefficient and the flow in gpm | The flow that produced the residual drop |
| Hydrant locations and elevations | Street addresses or hydrant numbers, a sketch, and the elevation of each hydrant relative to the site | Lets the designer correct pressures to the point of connection |
| Main size and pressure zone | Diameter of the main the hydrants sit on and the purveyor’s zone or gradient name | Confirms the test represents the main that will feed the building |
| Who ran it and who witnessed it | Purveyor crew, permitted contractor or engineer, plus any fire department or AHJ witness | The AHJ accepts tests from parties it recognizes |
| Season and system condition | Notes on pumps running, valves closed, tanks being filled or mains flushed nearby | Explains an unusually high or low reading and supports a request to accept an older test |
The elevation reference and the pressure zone carry the most weight in design. Without them the designer cannot show that the pressure at the hydrant is the pressure available at the building’s point of connection.
Figure 1: From Request to Submittal: Where the 12 Months Run
Where the Code Sets the Rule in Each State
The 12-month rule comes from NFPA 13, and the edition depends on which building code the state adopts, because the building code’s referenced standards chapter names the NFPA 13 year. The reviewer who accepts the test is the same authority that reviews the sprinkler working plans. In Maryland, the county building permit reviews sprinklers to NFPA 13 (2019) through the 2021 IBC, while the State Fire Prevention Code (NFPA 1, 2024) references NFPA 13 (2022).
| Jurisdiction | NFPA 13 edition and where the age rule sits | Who accepts the test (AHJ) | Filing the test travels with |
|---|---|---|---|
| New York State (outside NYC) | NFPA 13 (2022) Section 4.5.1.1, referenced by the 2024 IBC under the 2025 Uniform Code | Local code enforcement official | Building permit; sprinkler working plans and hydraulic calculations |
| New York City | NFPA 13 (2016) as modified by Appendix Q of the 2022 Building Code; the 12-month rule sits in Chapter 23 of the 2016 edition | Department of Buildings (DOB) plan examiner; Fire Department of New York (FDNY) on fire protection items it reviews | DOB NOW sprinkler work type filing with the hydraulic calculations |
| New Jersey | NFPA 13 (2022) Section 4.5.1.1, referenced by the 2024 IBC under the Uniform Construction Code (UCC), effective August 17, 2026 | Municipal fire protection subcode official | UCC construction permit, fire protection subcode technical section |
| Pennsylvania | NFPA 13 (2019) Chapter 4, referenced by the 2021 IBC under the UCC (January 1, 2026) | Municipal or third-party code official; Philadelphia Department of Licenses and Inspections (L&I) in the city | UCC building permit; Philadelphia fire suppression permit |
| Maryland | NFPA 13 (2019) Chapter 4 through the 2021 IBC at the county permit; NFPA 1 (2024) references NFPA 13 (2022) | County fire marshal or fire and life safety plan reviewer; State Fire Marshal where it has jurisdiction | County building permit, fire protection plan review |
| Delaware | NFPA 13 (2025) Chapter 4 under Regulation 701 (2026) | Office of the State Fire Marshal (Wilmington Fire Marshal inside the city) | State Fire Marshal plan review; the Preliminary Sprinkler Form asks for a flow test within the past 12 months on the water supplier’s letterhead |
Editions as adopted as of November 2026. Local amendments and purveyor rules are not shown.
DGA designs sprinkler water supplies and fire pumps, and orders and interprets flow tests, across New York, New Jersey, Pennsylvania, Maryland and Delaware. Project briefs get confirmation and preliminary code feedback within one business day. See where DGA works →
Who Can Perform a Flow Test
On a public main, the purveyor owns the hydrants and the valves, so the purveyor decides who opens them. Most purveyors in the region run the test with their own crew on request; some issue a permit that lets a licensed sprinkler contractor run it, often with a purveyor inspector watching. On a private main, the owner’s contractor runs the test, and in New York City that is typically a licensed master fire suppression piping contractor. The AHJ then decides whether the party that ran the test, and the date it ran, meet the standard.
Figure 2: Who Runs the Test and Who Accepts It, by State
| State | Public main: who runs the test | How it is requested | Who decides an older test is acceptable |
|---|---|---|---|
| New York City | Department of Environmental Protection (DEP) runs hydrant flow tests on the city distribution system | Request for Hydrant Flow Test filed online through DEP’s Permit and Review Information System (PARIS) | DOB plan examiner |
| New York State | The purveyor (municipal water department, water authority or private utility) runs or permits the test | The purveyor’s request form or letter | Local code enforcement official |
| New Jersey | The purveyor (New Jersey American Water, municipal utilities and municipal utilities authorities) runs or permits the test; Passaic Valley Water Commission, for example, takes a Hydrant Flow Test Application and lets the requester attend | The purveyor’s application; results are sent to the requester | Fire protection subcode official |
| Pennsylvania | Philadelphia Water Department runs tests on request; Aqua, Pennsylvania American Water and municipal authorities run or permit tests on their mains | Philadelphia: a letter of request with a utility plan or sketch, emailed with “FLOW TEST REQUEST” in the subject line | Code official; L&I in Philadelphia |
| Maryland | Washington Suburban Sanitary Commission (WSSC) offers fire flow tests on its system; Baltimore City Department of Public Works (DPW) runs tests and reports measured pressure and flow at named hydrants | WSSC Water’s online Fire Flow Test Application, which also takes payment (requests by mail ended September 2, 2026); Baltimore DPW Fire Flow Test Request Form with a site plan showing the connection | County fire marshal or plan reviewer |
| Delaware | The purveyor (Artesian, Tidewater, Veolia or a municipal utility) runs or permits the test | The purveyor’s application; the State Fire Marshal wants the result on the supplier’s letterhead | Office of the State Fire Marshal |
Where a purveyor permits a contractor to run the test, the permit usually names the hydrants, the date and the purveyor inspector, and the contractor’s record should say so. A test run on a public main without the purveyor’s knowledge is rarely accepted, and in several districts it is a violation. How the test is actually run and read is covered in DGA’s article on how a hydrant flow test is run and read under NFPA 291.
How a Flow Test Differs From the Documents It Is Confused With
Three documents get sent to reviewers in place of a flow test, and none of them satisfies NFPA 13 (2022) Section 4.5.1.1. Each measures or states something different, and each has its own use.
| Document | What it actually says | Why it does not replace a flow test |
|---|---|---|
| Purveyor availability or will-serve letter | The purveyor confirms it can supply the site and may quote a modeled pressure or a hydraulic grade; WSSC’s Hydraulic Information Sheet is one example and is a theoretical estimate at one point in the system | It is a commitment or a model, not a measurement. The hydraulic calculation needs two measured points, static and residual at a known flow |
| Fire pump acceptance flow test | Measures what the pump delivers at churn, rated flow and 150 percent of rated flow after installation | It tests the pump, not the main feeding it. The suction supply to the pump still comes from the hydrant flow test, as described in DGA’s article on what happens at a diesel fire pump acceptance test |
| NFPA 25 main drain test | Opens the system’s main drain and records the static and residual pressure at the riser gauge to detect a closed valve or an obstruction | The flow through a 2 in. drain is unknown and small, so the two readings do not define a supply curve |
The practical difference shows up in the calculation. A flow test gives the designer the two points needed to plot the supply curve against the sprinkler demand; DGA’s article on plotting sprinkler demand against the supply curve shows that step. A letter, a pump test or a main drain reading gives one number or the wrong number.
When a Current Flow Test Is Required
A current test is required at three points. The first is before working plans are submitted, which is the rule itself. The second is when a project stalls: if the plans were drawn on a 10-month-old test and the submittal slips 4 months, the test is 14 months old at submittal and the designer needs a new one or the AHJ’s written acceptance. The third is when the purveyor changes the system that feeds the site, such as a new pressure zone boundary, a replaced main or a booster station taken out of service; a test older than that change is not representative no matter its age.
Reviewers in New York City, New Jersey and Philadelphia check the test date against the submittal date as a matter of routine. Ordering the test early in design and submitting the working plans inside the window is cheaper than running it twice.
Common Misconceptions
“A 5-year-old test plus a purveyor letter is enough.” No. The letter confirms service; it does not refresh the measurement. The AHJ can accept the old test under the approval clause, but that is a decision the reviewer makes and documents, not a substitution the designer makes.
“The annual main drain test keeps the supply data current.” No. The main drain test under NFPA 25 (2023) Chapter 13 checks that the supply is still connected and the control valve is open. It does not measure flow, so it cannot replace the hydrant flow test behind a hydraulic design.
“The contractor can flow the street hydrants on the morning of the test.” Only with the purveyor’s permit. The hydrants belong to the purveyor, and a test run without its permission is usually refused by the AHJ and can draw a fine from the utility.
Who Needs to Act
| Who | One action |
|---|---|
| Owner | Order the flow test as soon as the sprinkler scope is known and keep the written record with the project file; a lapsed test delays the permit. |
| Engineer | Check the test date against the planned submittal date before building the hydraulic calculations, and ask the AHJ in writing if an older test must be used. |
| Sprinkler contractor | Put the test date, hydrant numbers, elevations and the name of the party that ran it on the hydraulic calculation sheet, not only in an attachment. |
| Purveyor | Issue the record with the pressure zone, main size and any abnormal system condition noted, so the AHJ can judge whether it still represents the supply. |
| Insurer | Ask for the test behind the design when underwriting; a current test with a margin above demand is the simplest evidence the water supply works. |
Key Takeaway: NFPA 13 (2022) Section 4.5.1.1 makes a sprinkler flow test current for 12 months, measured from the test date to the working plan submittal, with any extension granted by the AHJ and not assumed by the designer. The purveyor, or a contractor it permits, runs the test on public mains; the owner’s contractor runs it on private mains; and the record must carry the date, hydrant locations and elevations, static, residual, flow and the tester’s name to be usable.
Frequently Asked Questions
How old can a flow test be for sprinkler design?
No more than 12 months old on the date the working plans are submitted, under NFPA 13 (2022) Section 4.5.1.1. The AHJ can accept an older test, but that acceptance is the reviewer’s decision and should be in writing.
Can a sprinkler contractor run a hydrant flow test?
Conditional: on a private main, yes, since the hydrants belong to the owner. On a public main the contractor needs the purveyor’s permit, and many purveyors in New York, New Jersey, Pennsylvania, Maryland and Delaware run the test themselves on request instead.
Does a purveyor availability letter count as a flow test?
No. An availability or will-serve letter confirms the purveyor can serve the site and may quote a modeled pressure. A flow test is a measurement of static and residual pressure at a known flow, and the hydraulic calculation needs the measurement.
What happens if the test expires while the plans are under review?
Nothing, in most jurisdictions. The 12 months are measured to the working plan submittal, not to approval or installation. A test that was 11 months old at submittal is still a current test if the review takes longer.
More in Water Supply
- Do You Need a Fire Pump? How Engineers Decide (NFPA 20)
- Water Supply for Fire Protection: The Complete Guide
- What Is a Fire Pump Controller and Transfer Switch?
- When Can a Well or Private Source Supply Fire Protection?
- What Is Backflow Preventer Pressure Loss in Sprinkler Calcs?
- Split-Case vs In-Line vs Vertical Turbine: Which Fire Pump?
This article is general information, not a substitute for a project-specific code analysis. Code editions, local amendments, purveyor rules and reviewer practice change; confirm the adopted code and the authority having jurisdiction for the project.
Is the Flow Test Still Good for the Submittal?
Send the flow test record, the site address and the target submittal date. DGA checks the test age, the data the reviewer will look for and the margin against the sprinkler demand, and orders a new test or requests AHJ acceptance where needed. Project briefs get confirmation and preliminary code feedback within one business day.