The SMC 6940090 is a 1/4" FNPT threaded PVC check valve from the 694 Series, NSF certified with a Buna-N seal for reliable one-way flow protection in residential and commercial water systems. This compact valve prevents backflow and protects pumps, filters, and RO membranes from reverse pressure damage.
SPECIFICATIONS
SMC 694 Series Check Valve Technical Details
| Model Number | SMC 6940090 |
| Series | 694 Series |
| Connection Type | 1/4" FNPT x 1/4" FNPT |
| Body Material | PVC (Polyvinyl Chloride) |
| Seal Material | Buna-N (Nitrile Rubber) |
| Certification | NSF Certified |
| Flow Direction | One-way, inline check valve |
| Application | Water filtration, RO systems, pump protection |
INSTALLATION & USE
Installing the SMC 6940090 Check Valve
- Apply thread sealant tape (PTFE) to male NPT fittings that will thread into both 1/4" FNPT ports on the valve body.
- Install the check valve in the correct flow direction as indicated by the arrow molded into the PVC body, typically after pumps or before storage tanks.
- Hand-tighten fittings, then use a wrench to snug an additional quarter turn. Do not over-torque PVC threads.
- Pressurize the system slowly and check all threaded connections for leaks before leaving the installation unattended.
COMPATIBILITY
System Integration
The SMC 6940090 check valve integrates with any 1/4" FNPT threaded system including reverse osmosis units, booster pumps, water filtration housings, and storage tank lines. The Buna-N seal is compatible with chlorinated water, sediment-filtered feed water, and product water up to 100°F. NSF certification ensures materials meet drinking water safety standards. This valve is a direct replacement for other SMC 694 Series check valves and comparable 1/4" FNPT check valves from other manufacturers.
🔧 Pro tip: Always install check valves with the arrow pointing in the direction of desired flow. If backflow persists after installation, debris may be lodged in the seat—disassemble, clean the Buna seal and PVC seat, and reassemble with fresh thread tape.
