Tube Identification in SmartTech and Legacy Dryers

Follow Avatar BRANDON BOYL
Updated : Created :
In this article


Identifying Tube Numbers in Water Seal Dryers


In the Smart Tech and older generations of dryers with water sealed compressors some of the ¼” tubing is identified with number or letter markings. This document will explain the meaning of the numbers and aid in identifying if they are connected properly.



Circled above are examples of the identification markings on the tubing. Note that the tubes are not marked with the same identifier on both ends but instead each end is identified by where it should be connected to.

  • Tubes identified with “A” or “B” connect to the A or B side of the system controller block. The sides of the controller block are stamped with A and B respectively near the push connect fitting on each side.
  • Tubes with a single digit number connect to the system pressure regulator. The system pressure regulator ports should be identified with a sticker on the back of the regulator. If the regulator has been replaced or the identification is missing, the regulator has a single input port and 3 output ports. The input port is number 1 and the output ports are 2, 3 & 4.


  • Tubes with double-digit identification connect to a solenoid valve. Each solenoid valve can be identified either by referencing the electrical schematic and comparing the color of wires connected to it with what is shown in the schematic or in some older models the solenoid valves may have identification labels next to them.  In the schematic each valve is identified as “SV” for solenoid valve and the number. As an example, a tube marked with “41” would connect to the humidity shutoff valve, SV4, port number 1. “52” would connect to SV5 water eject valve port number 2 etc. Each of the small solenoid valves has markings formed in the brass body identifying the main ports 1 and 2. The port 3 is located on the top of the coil and may have an adapter fitting or a sealing screw installed depending on the usage.