What component should be installed to enable service or testing of pressure sensors downstream of the source valve?

• A. D.I.S.S. fitting
• B. Check valve
• C. Demand check fitting
• D. Shutoff valve

Answer: (C)

The key idea is having a setup that lets you access and test the downstream pressure without allowing gas to flow backward toward the source. A demand check fitting provides a built-in test port and a one-way valve, so you can connect a pressure gauge or testing device to the downstream side and verify sensor readings while the system remains protected from reverse flow when not testing. It ensures reliable testing of the downstream sensors without compromising the upstream supply.

Other options don’t offer that combination: a DISS fitting is about safe, correct connections but not specifically a testing port; a plain check valve stops reverse flow but provides no testing access; a shutoff valve can isolate but also doesn’t supply a test port or backflow protection needed for testing sensors.