[77newell]

There is a check valve at the outlet of the drier, so yup, Richard, you got that right. As far as I know there is no other check valve(s) until after the "service" or "wet" tank (two names, one tank). Each of the brake tanks has a check valve on the inlet supply from the "service" tank so they are isolated from each other. That way a single leak associated with one of them doesn't effect the other, but that leak will tend to also deplete the "service" tank. As long as the supply exceeds the leakage rate the pressure will be adequately  maintained and the emergency brakes won't deploy. Your compressor may cycle a lot but you won't be stopped. This appears to be Brad's situation.

Richard: the only time I'm not confuseded is when I'm wrongerer.