most vehicle has a sticker under hood that is a "road map" for vacuum hoses, shed a good falshlight in the area and get to work,
Depends on the vehicle and how it is set up. Some are connected before the throttle plate (ported vacuum or delayed vacuum) and some are connected after the throttle plate (straight manifold vacuum). More info needed.
the line is connected to the carburettor if you have one or to the intake manifold after the throttle valve. The purpose is to connect intake vacuum to the booster.
A manifold vacuum source, anywhere below the throttle plates.
The vacuum hose on a 1994 GMC Safari is connected to the intake manifold. This is located to the left of the throttle body.
on the back of the throttle body or intake port.
Connect the line to a source that is above the throttle body on the carb. It should be a source that has no vacuum at idle.
The hissing may be due to a disconnected vacuum line. Look for a loose vacuum hose and/or a tube on/near the throttle where it might connect to.
Look on the carb for a small vacuum source above the throttle body. You would want one that has no vacuum at idle.
There should be a vacuum source on the carb above the throttle body that gives spark ported vacuum. You can connect a tube from this source to the distributor.
On the drivers side below battery. From near the front bumper the Evap cannister is connected by vacuum hoses to evap solenoid than another vacuum hose to valve which is than connected to throttle body.
It comes out the left side,towards the rear of the tranny. The metal line runs up on top of the transmission to a port behind the throttle body. Other vacuum line are also connected to that port.
Your question is to vague to answer. If you connected a vacuum hose to a water hose you would be ingesting water into the engine.