Sabretooth:
Sorry, I don’t quite understand, Why are you getting pressure when you connect the Suzzie? Yes there is always a little back pressure but if you pump the brake a couple of times prior to disconnect the pressure is released.
All the trailers I ever used had a handle at the base of the connectors in order to close the air lines. cutting off the air for disconnecting and reconnecting. Trailer braking systems have a one way valve system so the air is only coming from the unit air tank !! And once the handle is turned the air is closed off, so there should be no pressure building up or stored in the lines.
Plus allowing the air to flow while attempting to connect or disconnect is dangerous ?
As soon as you start a unit the air pressure on the unit builds up. If its too low to operate the handbrake or gearbox?? the unit wont move so inevatibly there will be some pressure on the airline at all times. The reason it doesnt drop is the airlines have valves on so they dont release the air untill the fittings counter part is connected. However as You pish the fittings together the valve is partialy opened hence back pressure that trys to push the fitting apart.