NFPA 20 - Check valve on fuel return line

[Piper888]

Hello,

Can anyone explain the basis of the check valve for fuel return line to be as per engine manufacturer requirement instead of being a hard requirement in NFPA 20 and how does engine manufacturers decide if a check valve is required or not?

11.4.4.3.1 A check valve, as specified by the engine manufacturer, shall be permitted to be installed in the fuel return line only when required by the engine manufacturer.

 

[LittleInch]

As noted by others I think this depends on the location of the fuel tank relative to the engine. Above it and the return line is below the fuel level, then they fit it, below, they probably don't.