[Excaliber]

Not all the solenoid/electric type line locks require constant voltage. After you've pumped up and locked the system you can remove power to the solenoid. Simply use a momentary switch for the initial engagement. Some even have a system that alerts you via a light, your horn, maybe a buzzer that the system pressure has dropped below a certain threshold.

While the lawyers and the Government won't allow them from a legal stand point, never the less, many "Motor Homes" use them for a long term auxillary holding system.