A fire protection check valve lets water flow in one direction only and closes on its own when flow stops or reverses. On a water-based fire network it goes on the fire pump discharge, on the pump bypass, on the fire department connection (FDC) line and on every additional water supply. You select it by end connection, the highest pressure at that point and the size that comes out of the hydraulic calculations.
AZEIDK supplies two American Fire Control (AFC) models in Saudi Arabia: the A-3150 flanged swing check valve and the A-3500 grooved swing check valve. This article compares the two using the figures in AFC’s own submittal, shows where a check valve is required in the pump room and on the FDC, and lists what to check before the BOQ is approved.
Key takeaways
- The A-3150 (flanged) and A-3500 (grooved) both come in 2 to 12 inch sizes and are UL Listed and FM Approved according to the AFC catalog.
- Maximum working pressure is 300 psi for the flanged valve and 350 psi for the grooved valve; maximum test pressure is 600 psi and 700 psi.
- NFPA 20 requires a listed check valve in the pump discharge assembly, followed by a listed indicating valve on the system side.
- NFPA 13 requires a listed check valve in each fire department connection, with no shutoff valve in the FDC piping.
- The submittal states the A-3500 can be installed horizontally or vertically. It gives no orientation for the A-3150, so confirm with the manufacturer before using it in a vertical line.
In this article
- What does a swing check valve do in a fire network?
- Flanged A-3150 or grooved A-3500: how do the numbers compare?
- Where does the check valve go at the fire pump?
- Check valves on the fire department connection and multiple supplies
- What should you check in the BOQ before ordering a check valve?
- Common fire protection check valve installation mistakes
- Frequently asked questions
- Conclusion
What does a swing check valve do in a fire network?
Inside a swing check valve is a disc (clapper) hung on a hinge pin. Forward flow pushes it open. When flow stops, or pressure on the downstream side becomes higher, the disc drops back onto its seat and closes. It needs no power, and it is not an isolation valve. Isolation is the job of control valves such as AFC OS&Y gate valves.
On a fire network the check valve does three practical jobs. It holds system pressure after the fire pump stops. It stops water pumped in through the FDC, or from another source, from flowing back toward the pump or tank. And it separates water supplies so one source cannot feed into another. Do not confuse it with a wet alarm check valve: that is a check valve with an alarm port and a dedicated trim, covered in our article on the AFC ACV-300 wet alarm check valve.
Flanged A-3150 or grooved A-3500: how do the numbers compare?
The figures below come from the official AFC valve submittal published on the AZEIDK website and from the two product pages. Use them for first comparison; the approved datasheet in the project file is the final reference.
| Item | A-3150 (flanged) | A-3500 (grooved) |
|---|---|---|
| Sizes | 2, 2.5, 3, 4, 6, 8, 10, 12 in | 2, 2.5, 3, 4, 6, 8, 10, 12 in |
| Max working pressure | 300 psi (21 bar) | 350 psi (24 bar) |
| Max test pressure | 600 psi (42 bar) | 700 psi (48 bar) |
| Ends | Flanged to ANSI B16.1 Class 125 or ANSI B16.42 Class 150 | Grooved to AWWA C606 or metric dimensions |
| Body | Ductile iron ASTM A536 65-45-12 | Ductile iron ASTM A536 65-45-12 |
| Disc | Ductile iron with EPDM disc ring | Stainless steel 304 with stainless steel spring |
| Seat | Bronze | Bronze C95400 |
| Orientation | Not stated in the submittal | Horizontal or vertical, indoor or outdoor |
| Coating | Fusion-bonded epoxy inside and out to ANSI/AWWA C550 | Fusion-bonded epoxy to ANSI/AWWA C550, or paint on request |
| Reference standard | Meets or exceeds AWWA C508 | Not stated |
| Operating temperature | 0 to 80 °C | 0 to 80 °C |
Weight and length matter in the pump room
The biggest practical difference is weight and length. According to the submittal tables, a 6 inch flanged valve weighs about 65 kg with a 14 inch laying length, while a 6 inch grooved valve weighs about 20.3 kg with a 10.63 inch length. At 10 inch the gap is about 185 kg against 56.3 kg. That affects the space between valves in a tight pump room, hanger and support design, and how easy the valve is to remove for service.
When does each type make sense?
- Flanged A-3150: when the pump, the adjacent valves or the main lines are flanged, so the valve bolts in without a transition piece. The mating flange must match the standard and class stated in the submittal.
- Grooved A-3500: when the network is grooved, when weight and space are tight, or when the maximum system pressure is above 300 psi but not above 350 psi. The pipe groove must match the valve’s groove standard, and the grooved couplings must be listed for the same pressure.
- Either way: compare the valve’s maximum working pressure with the highest pressure at the point where it will be installed, including the highest pressure the pump can produce there, according to the approved calculations.
Where does the check valve go at the fire pump?
NFPA 20 is a technical standard the designer adopts and Civil Defense accepts as part of the project requirements; it is not a stand-alone legal text. The Saudi Fire Protection Code SBC 801, 2024 edition, has been mandatory since 30 June 2025, and its referenced-standards chapter sets which edition of each standard applies. A typical discharge arrangement, as listed in the Los Angeles Department of Building and Safety NFPA 20 (2019) plan check sheet, runs in this order:
- Pump outlet, then the pressure relief valve where one is required, installed downstream of the pump and before the check valve.
- A listed check valve in the discharge assembly.
- The pressure sensing line connection for the main pump and jockey pump controllers, made between the discharge check valve and the discharge control valve.
- The test header connection, which CSE also places between the discharge check valve and the control valve so the pump can be tested with the control valve closed.
- A listed indicating control valve on the system side, so the pump can be isolated for service.
If the pump has a bypass, it also needs a check valve (an item on the same LADBS sheet), and CSE adds an isolation valve on each side so the check valve can be isolated and serviced. For tanks, suction lines and controllers, see our guide to fire pump rooms in Saudi Arabia.
Check valves on the fire department connection and multiple supplies
The fire department connection (often called the Siamese connection on site) lets Civil Defense crews pump water into the system from their trucks. NFPA 13 (2022 edition) sets clear rules for it:
- Install a listed check valve in each fire department connection, in an accessible location (section 16.12.6.1).
- Do not install a shutoff valve in the FDC piping.
- Do not connect the FDC to the suction side of the fire pump; connect it on the system side.
- Where there is more than one water supply, install a check valve in each supply connection (section 16.9.4.1, as quoted by QRFS).
NFPA 14 has a matching requirement for the FDC check valve on standpipe and hose cabinet systems. Drainage between the FDC and the check valve, and the valve’s position relative to the building wall, are details the designer sets on the approved drawings.
What should you check in the BOQ before ordering a check valve?
Most consultant comments on check valves are not about the valve itself but about how it fits with everything around it. Check these points before the purchase order goes out:
- Size: from the hydraulic calculations and the discharge line size, not from the pump flange size alone.
- Pressure: the highest pressure at that point against 300 psi (flanged) or 350 psi (grooved).
- Ends: flange class and drilling, or groove standard and coupling type.
- Orientation: horizontal or vertical, and confirmation in the datasheet, or in writing from the manufacturer, that the model allows it.
- Listing and approval: search the model code in UL Product iQ and the FM Approvals guide. The AFC submittal labels the grooved valve A-3500 on one page and AG-3500 on another with identical specifications, and the copy of the UL listing included in it (file EX28962) names A-3150, AG-3500, AF-3500, AFG-3500 and AFG-3501. Match the code on the valve nameplate and the submitted datasheet to the listed code before approval.
- Documents: datasheet, pressure test report and material certificate in the submittal package for the consultant. Product documents are on our technical documents page.
AZEIDK’s technical selection of systems and equipment team can review these points against your BOQ before you order.
Common fire protection check valve installation mistakes
- Installing the valve against the arrow cast on the body, so it blocks flow from the pump instead of blocking backflow.
- Specifying a flanged model in a vertical line without the manufacturer confirming that the model allows vertical installation.
- Putting a shutoff valve in the FDC piping, which NFPA 13 does not allow.
- Connecting the pressure sensing line or the test header in the wrong position relative to the check valve.
- Mixing metric grooves with AWWA C606 grooves without checking that valve, pipe and coupling match.
- Skipping the internal inspection. NFPA 25 (2023 edition, section 13.4.2.1, as quoted by QRFS) calls for check valves to be inspected internally every 5 years, with internal parts cleaned, repaired or replaced according to the manufacturer’s instructions.
Frequently asked questions
What is the difference between a check valve and an alarm check valve?
Both stop backflow. An alarm check valve also has an alarm port and trim that signal when water flows to the sprinklers. A plain swing check valve gives no alarm.
Can an AFC check valve be installed vertically?
The AFC submittal states the grooved A-3500 can be installed horizontally or vertically. It does not state an orientation for the flanged A-3150, so get the manufacturer’s confirmation before using it in a vertical line.
Which model has the higher pressure rating?
The grooved A-3500, at 350 psi maximum working pressure, against 300 psi for the flanged A-3150, according to the AFC catalog.
Is a check valve required on the fire department connection?
Yes. NFPA 13 requires a listed check valve in each fire department connection and no shutoff valve in its piping.
How often is a check valve inspected internally?
Every 5 years under NFPA 25, in addition to the manufacturer’s instructions and the approved maintenance plan.
Conclusion
Choosing a check valve starts with where it goes: pump discharge, pump bypass, FDC line or an additional supply. Then match the end connection to what is around it, compare its rating with the highest pressure at that point, and confirm orientation and listing for the exact model. Of the two AFC models available, the A-3150 suits flanged lines, while the A-3500 suits grooved networks, tight spaces and pressures up to 350 psi.
Preparing a pump room or riser BOQ? Send us the sizes, system pressure and end connections, and we will recommend the right AFC check valve with its datasheet and submittal. Talk to the AZEIDK team
