Cleaning overflow siphon

[Newms118]

I have a Herbie overflow set up in my tank and wanted to know how to or how often should the siphon pipe be cleaned? My emergency overflow pipe runs dry so I know that doesn't need cleaning.

I figured I could try to unscrew the screen and use some type of pipe cleaner to get to the gate valve where I presume the most build up has occurred. Or conversely. I could run the pipe cleaner from the bottom and not mess with the pipe screen.

Any help is appreciated.