You can Wetdown the tunnel from Stack Management.

1. On the Touch POS, Touch IT or Touch ES, open WashConnect.
2. On the StackNControl menu, select Stack Management.
3. Tap or click the Wetdown button. 

The Wetdown takes place in tunnel.

NOTE: Wetdown function is available on the Tunnel Master Jr. and WBC controllers. Third party controllers may not support this function.