Yes that's the setup, normally there is a mechanical non return valve too at the end of 13 but that one used to wear out and if the exhaust valve doesnt close well when the system gives the command to the compressor and the air supply valves to inflate the air leaves the system at the exhaust...here's the operational scheme too, it's not a very complicated system and once you understand how it works it's easy to troubleshoot, eventually read the whole story in RAVEwhen the suspension is lowered the air from the bags travel back along pipes 12 & 14 back to the valve block and get expelled through pioe 13???