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NFPA 14 §7.2.3NFPA 25 §6.4NEW

Pressure-Regulating Valves (PRV / PRD / PCV)
The Three Devices That Aren't All The Same Thing

Pressure-Reducing Valve, Pressure-Control Valve, Pressure-Restricting Device — three regulating products that get called "PRV" in casual conversation, plus a fourth device people confuse with all of them: the Pressure Relief Valve, which is a different animal entirely. The regulating-vs-relief distinction killed three firefighters at One Meridian Plaza in 1991. Here's the real taxonomy, what each one does, when each one is required, and how to test them.

By Stanislav Samek, Samektra · 11 min read · Reviewed May 2026

Bermad PRVs in service. Note: each valve has a control-valve tag, electric supervisory module, and isolation OS&Y on inlet and outlet. The diagonal pipe segment between the two PRVs is the riser progressing to the next floor.

Why the distinction matters — the One Meridian Plaza lesson

February 23, 1991. A 38-story office tower in Philadelphia caught fire on the 22nd floor. The fire department arrived, climbed to the floor below, and connected hand lines to the standpipe outlets. They got 60 to 65 psi. They needed approximately 100 psi to develop adequate stream on a 2½ in handline at the seat of the fire. They tried lower floors. Same result.

The pressure-reducing valves on the standpipe were factory-set to deliver about 60 psi at each outlet — well below what was needed. The valves were "working" correctly: they regulated to their setpoint. The setpoint was just wrong. And in the 18 years between commissioning and the fire, no one had ever flow-tested the PRVs to verify the actual delivered pressure at each outlet under design flow. Three Philadelphia firefighters died.

The post-incident investigation drove the modern NFPA 25 §6.4 rule: every PRV must be flow-tested at acceptance, partially flow-tested annually, and fully flow-tested every 5 years at design flow. The visual that the valve is in place is not enough. Test pressure at the outlet, document it, compare against acceptance values.

The three flavors of pressure-regulating device

NFPA 14 §3.3.18 defines "Pressure-Regulating Device" as the umbrella term. Underneath are three distinct products with different mechanisms and different use cases:

1. Pressure-Control Valve (PCV) — §3.3.18.1

Per NFPA 14 §3.3.18.1: a pilot-operated valve that reduces downstream pressure to a specific value under BOTH flowing (residual) and non-flowing (static) conditions. The modern, NFPA-preferred term for a pilot-operated regulating valve.

Identifying feature: pilot dome on top of the body + sensing line that loops from the downstream port back to the pilot.

2. Pressure-Reducing Valve (PRV) — §3.3.18.2

Per NFPA 14 §3.3.18.2: reduces downstream pressure under BOTH flowing and non-flowing conditions. Same functional definition as a PCV — and in field practice the two terms are used interchangeably. Most manufacturer tags say "Pressure Reducing Valve."

Used: standpipe outlets where static > 175 psi (NFPA 14 §7.2.3); high-rise sprinkler zones where supply pressure exceeds component ratings (NFPA 13 §16.9). Brands: Bermad 720 / FP-42T, Watts 909, Cla-Val 90-01, Reliable LFD. UL listing: UL 1468.

3. Pressure-Restricting Device — §3.3.18.3

Per NFPA 14 §3.3.18.3: reduces downstream water pressure under FLOWING conditions ONLY. A fixed orifice, plate, or restricting hose-valve. Static pressure passes through unchanged — a closed outlet still sees full upstream pressure.

Used: sprinkler-only piping where every component is rated for full upstream pressure. NOT acceptable as the sole regulating device on standpipe hose connections where static pressure matters. Identifying feature: no pilot, no diaphragm, no sensing line — usually a flat plate between flanges or built into a hose-valve body.

The three are visually similar. PCVs and PRVs both have a pilot dome on top of the body and a sensing line. The pressure-restricting device is much smaller, often hidden inside a hose-valve body or invisible between flanges. Always read the manufacturer tag — the words "control," "reducing," or "restricting" on the tag tell you which type you actually have.

Pressure RELIEF Valves — a different animal entirely

A Pressure-Regulating Device controls downstream pressure — it sits in the flow path and modulates how much pressure passes through.

A Pressure Relief Valve does something different: it sits as a side branch off the main flow path and opens to dump water when pressure on the upstream side exceeds a safety setpoint. It’s an over-pressure protection device, not a regulator. Field technicians regularly conflate the two; the words sound similar and both have "pressure" in the name. They are not the same thing.

Where you’ll see relief valves in fire protection

  • Standpipe relief — NFPA 14 §7.2.5. A relief valve is required on the standpipe when pressure could exceed 350 psi at any point. Two common causes of over-pressure: gravity loading in tall buildings (a 30-story standpipe at the bottom can see 200+ psi of head from the water column above), and fire-pump churn (when the pump runs at no-flow and dead-heads against a closed system).
  • Fire-pump casing relief — NFPA 20 §4.20 + §4.21. Every fire pump has a small relief valve on the discharge casing. When the pump runs at churn (no flow), the casing relief bleeds 6-8 gpm continuously to prevent the impeller from overheating. The water typically discharges to a drain or floor sink. Don’t plug it "to stop the leak" — that’s the design.
  • Pressure-tank relief. Atmospheric pressure tanks and bladder tanks both require a code-required relief valve to protect against over-pressurization during fill or thermal expansion.
  • Backflow-preventer relief port. RPZ backflow preventers have a built-in relief valve that opens if either check fails — visible water discharge from the relief port is the signal that the device has failed and is doing its job.
Quick visual ID: regulating valves discharge through their downstream pipe, in line with the flow. Relief valves discharge to a drain, floor sink, or atmosphere through a side port. If you see a valve with a discharge pointed at the floor or hanging out into the room, it’s a relief valve. If the valve is in the middle of a pipe run and the same pipe leaves the other side, it’s a regulator.

ITM cadence is also different. NFPA 25 §6.4 covers regulating valves (PRV/PCV/restricting). Relief valves on standpipes are tested annually for operation per NFPA 25 §13.5; fire-pump casing relief is verified during the annual pump test by observing flow during churn. A casing relief that’s NOT discharging during churn is failed shut and the pump is at risk; a casing relief discharging during full flow is failed open and the pump is wasting capacity.

How a pilot-operated PRV actually works

Inside the valve body, a flexible diaphragm separates the inlet from the outlet. The diaphragm is held against its seat (closing the flow path) by water pressure on the upper chamber, fed from the inlet through a small port and modulated by an external pilot.

  • Downstream pressure is sensed through a small sensing line that loops from the outlet flange back to the pilot.
  • If downstream pressure RISES above the pilot setpoint, the pilot bleeds water out of the upper diaphragm chamber. The diaphragm rises off the seat, restricting flow, until downstream pressure equals setpoint.
  • If downstream pressure FALLS below setpoint, the pilot fills the upper chamber. The diaphragm seats harder, opening the flow path, until downstream pressure rises to setpoint.
  • The pilot setpoint is adjusted by a screw on top of the pilot — typical ratio ~¼-turn ≈ 5-10 psi. Always document setpoint changes with a dated tag on the valve.

The whole system is mechanical — no electronics, no power. A PRV does not signal the FACP if it’s closed or stuck (unlike a control valve, which has a tamper switch). That’s why annual visual + 5-year flow test is the only way to verify performance.

NFPA 25 §6.4 ITM cadence

  • Quarterly: visual on every PRV — body intact, no leaks, sensing line attached, isolation valves in correct position, tags legible.
  • Annual partial-flow test: open the valve to a representative flow (a hose stream from the test outlet typical), record static and residual at the outlet downstream of the PRV, compare to acceptance values. NFPA 25 §6.4.1.1
  • 5-year full-flow test: flow at the design flow rate (typically 250 gpm minimum per outlet for Class I standpipe; 500 gpm for the most-remote outlet), record static and residual, compare to acceptance values. Variation greater than ±10% from acceptance triggers investigation. NFPA 25 §6.4.1.2
  • Acceptance: at install, every PRV is flow-tested and the as-tested pressure values are recorded. These values become the baseline for every future test. If the acceptance record is missing, the AHJ may require a new acceptance-style test before the building gets a CO.
Field-inspector tip: the partial-flow test is regularly skipped because it requires water discharge and access to the test outlet. The 5-year is regularly skipped because it requires more flow than building drains can handle. Both skips have caused real-world deaths. If the acceptance record + 5-year records are missing, the building has an unknown-pressure standpipe.

Field-inspector quick check

  1. Identify the type. PCV, PRV, restricting device, or RELIEF valve? Read the tag. If the tag is missing, document and flag. Discharge to drain = relief; discharge in line = regulating.
  2. Visual integrity. No leaks at the body, no leaks at the sensing line, no leaks at the pilot adjustment screw. No corrosion at the diaphragm flange. Sensing line not pinched, kinked, or cut.
  3. Setpoint documentation. Setpoint tagged on the valve? Date of last setpoint adjustment + initials? If not, mark as deficient.
  4. Isolation valves. OS&Y or butterfly on each side, in the correct position (open). With tamper switches if NFPA 25 §13.3 requires.
  5. 5-year test record. Last full-flow test < 5 years ago? Acceptance test on file? If neither, flag for the AHJ.
  6. Acceptance documentation. The original commissioning record showing as-tested pressure values at each outlet. Without this, future tests have no baseline to compare against.
  7. Casing relief on the fire pump. Walk the pump room during churn — water should be visibly discharging from the casing relief to the floor drain. If dry, the relief is failed shut.

Watch: Bermad PRV reset procedure

Bermad's official walkthrough on resetting the FP-42T / 42T-20 fire-protection pressure-reducing valve — the same family of valves shown in the hero photo at the top of this article. Useful when a PRV has been over-pressured, the pilot has tripped, or an annual flow test moves the setpoint and you need to re-establish the design downstream pressure.

BERMAD Water Control Solutions — official manufacturer video. Always verify reset procedure against the specific model installed; FP-42T and FP-720 have different pilot adjustments.

▶ Watch on YouTube

See sprinkler system inspections and maintenance on What The Fire Code.

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Frequently Asked Questions

Is "pressure-regulating valve" the same as "pressure-reducing valve"?
No — and the distinction matters. NFPA 14 §3.3.18 defines "Pressure-Regulating Device (PRD)" as the umbrella term covering three sub-categories: (1) Pressure-Control Valve (PCV) — pilot-operated, reduces downstream to a setpoint under both flow + no-flow [§3.3.18.1]; (2) Pressure-Reducing Valve (PRV) — reduces downstream under both flow + no-flow [§3.3.18.2] — effectively the same function as a PCV; the labels are used interchangeably in field practice; (3) Pressure-Restricting Device — reduces downstream under flow ONLY [§3.3.18.3]. On a standpipe outlet where static pressure matters, only a PCV/PRV works — a restricting device leaves full static pressure on the closed outlet.
What about a "Pressure Relief Valve" — is that the same thing?
NO — completely different animal. A Pressure-Regulating Device controls DOWNSTREAM pressure. A Pressure RELIEF Valve dumps water to atmosphere when UPSTREAM pressure exceeds a safety setpoint — over-pressure protection, not regulation. Two main fire-protection contexts: (1) NFPA 14 §7.2.5 requires a relief valve on the standpipe when pressure could exceed 350 psi at any point (typically from gravity loading in tall buildings or fire-pump churn). (2) NFPA 20 §4.20 + §4.21 require a casing relief valve on every fire pump — a small valve on the pump casing that bleeds 6-8 gpm continuously when the pump is running at churn (no flow), preventing the pump from overheating. If you see "PRV" stamped on a body and you can't tell which kind, look at the discharge: regulating valves discharge through their downstream pipe; relief valves discharge to a drain or atmosphere.
When does NFPA require a PRV?
NFPA 14 §7.2.3: any 2½ in standpipe outlet where static pressure exceeds 175 psi must have a pressure-regulating device that limits both static and residual to safe values for fire-department hose use. The same threshold applies in NFPA 13 §16.9 for high-rise sprinkler designs where supply pressure exceeds component ratings. The FD hose-coupling pressure rating (typically 175 psi for 2½ in NHT couplings + handlines) is what drives the limit.
What goes wrong with a PRV?
Three failure modes account for most issues. (1) Stuck shut — diaphragm has set against the seat after years of no operation; FD opens the outlet and gets 60 psi or less. (2) Stuck open — pilot has failed; downstream pressure equals upstream, hose blows off the coupling. (3) Drifted setpoint — pilot adjustment changed without documentation; valve regulates but to the wrong number. The 5-year flow test catches all three.
How is a PRV tested?
NFPA 25 §6.4 — partial flow test annually, full-flow test every 5 years. Full-flow test: discharge through a flow-test header at design flow (typically 250-500 gpm depending on the standpipe class), measure the residual pressure at the test outlet, compare against the original acceptance test (or the design value if no acceptance record exists). Variation more than ±10% from acceptance values warrants investigation. Document static AND residual at the test outlet.
Can I use a pressure-restricting device instead of a PRV?
Only on sprinkler-only piping where the design considers full upstream pressure on every component. For standpipe outlets where the FD will connect a hose, no — restricting devices fail the standpipe use case because a standpipe sits at static pressure when no one is flowing water, and the restricting orifice only drops pressure under flow. The hose connection sees full static pressure when first opened. NFPA 14 §7.2.3 effectively prohibits restricting devices alone on hose connections above 175 psi static.
What is the One Meridian Plaza fire and why does it matter for PRVs?
A 38-story office building fire in Philadelphia, February 23 1991. Three firefighters died. The post-incident NIST + NFPA investigation found that PRVs on the standpipe at the fire floors were factory-set to deliver only 60-65 psi to the fire-department hose connections — far below the ~100 psi the FD needed for adequate flow on 2½ in handlines at the seat of the fire. The valves "worked" — they regulated to their setpoint — but the setpoint was wrong, and nobody had ever tested the valves at design flow conditions. The case is now the textbook reference for why NFPA 25 §6.4 requires the 5-year flow test, and why every PRV setpoint must be verified at acceptance + every 5 years.
How does a Bermad/Watts/Cla-Val PRV actually work?
Pilot-operated diaphragm. Inside the body, a flexible diaphragm sits across the flow path. A small pilot valve on the side senses downstream pressure through a sensing line. When downstream pressure rises above the setpoint, the pilot reduces fluid pressure on the upper side of the diaphragm, the diaphragm lifts, more flow passes; when downstream pressure drops below setpoint, the pilot pressurizes the upper diaphragm chamber, the diaphragm seats, less flow passes. Mechanical, no electronics. Setpoint is adjusted by turning the pilot screw — typically ¼-turn = 5-10 psi change.
How are the three styles tagged in the field?
PRV is the most common — manufacturer tag will say "Pressure Reducing Valve" or "Pressure Reducing Pilot." Look for the pilot dome on top of the body and the sensing line that loops down to the downstream side. Pressure-restricting devices are often hidden inside hose-valve bodies or sit as a separate orifice plate between flanges — much smaller, no pilot. Pressure-control valves look like PRVs but the tag will say "PCV" or "Pressure Sustaining" — they sense UPSTREAM pressure to hold downstream constant.

References

1. NFPA 14 (2019): Standpipe and Hose Systems, §3.3.18 + §7.2.3.

2. NFPA 13 (2022): Installation of Sprinkler Systems, §16.9 (high-rise PRVs).

3. NFPA 25 (2023): ITM of Water-Based Fire Protection Systems, §6.4.

4. UL 1468: Direct Acting Pressure Reducing and Pressure Restricting Valves.

5. NIST Technical Investigation Report — One Meridian Plaza Fire (1991).

6. Bermad / Watts / Cla-Val technical bulletins on pilot-operated PRV adjustment.

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Discussion (3)

You
MT
Mike T.High-rise FP Inspector — 18 yr· 4 days ago

The single biggest PRV problem I see is the 5-year flow test that gets skipped year after year. The valve sits there looking great, gauges read fine, but the diaphragm has stuck or the pilot has drifted. When the FD finally needs the standpipe at floor 35, they get either 60 psi (PRV stuck closed) or 250 psi (PRV stuck open) — and either is bad. One Meridian Plaza in '91 was the case study. Don't let your building be the next one.

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SamektraSafety Management & Training· 3 days ago

Right — NFPA 25 §6.4.1 is explicit that the 5-year test must verify each PRV at each outlet flowing at design conditions. The post-Meridian Plaza ASTM 869 study found about 40% of tested PRVs in older buildings either restricted to too low or failed to restrict. Annual visual gets overlooked because the valve looks identical whether it works or not.

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LP
Linda P.Sprinkler Designer — Atlanta· 2 weeks ago

Confusion between pressure-reducing and pressure-restricting devices comes up on every plan review. Pressure-restricting (the orifice plate type) is cheap and code-acceptable in some sprinkler-only installations, but you can NOT use it on a standpipe outlet where static pressure matters. The standpipe sits pressurized at 200 psi all day — the FD opens an outlet, that 200 psi blows the hose off the connection. PRV is required when static exceeds 175 psi. Spec it right the first time.

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RH
Ron H.NICET IV Inspector· 3 weeks ago

We mark every PRV with a tag showing the setpoint, install date, and last 5-year flow test. Some AHJs in our area are starting to require this level of documentation. Helps when the next inspector — or the FD — needs to know what they're working with. Bermad and Watts both publish setpoint adjustment procedures; keep a copy in the riser room.

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