How do the boat lifts that use air work? If they have a check
valve to let water out the bottom when they force air in, how
do they let the water back in to sink it? I thought maybe a
solenoid valve, but don't see any wires running to the float
tanks...only what appears to be an air hose. Is HydroHoist
the only lift that uses air? I read that they have a patent,
but they can't have a patent on the concept of using air
to lift a boat can they?