Loose or worn belt.
You don't. Serpentine belts are adjusted by a spring loaded device called a belt tensioner. If you belt is loose, then the tensioner is broken.
Adjusted too loose, belt is glazed over and worn out, replace it.
When a serpentine belt is loose it means either the belt has stretched and needs replacing, or the idler tensioner is defective and needs replacing, or both.
either the belt is worn to the point of breaking or its very loose
If the belt is too loose or not there then yes - the water pump runs off the serpentine belt. If the belt is too loose or not there then yes - the water pump runs off the serpentine belt.
If you checked the belt and you think it is loose ,change it. It has a tensioner built in that sets the tension when the belt is installed.
A 1995 Geo Prism may experience squealing if the power steering pump is failing or the serpentine belt is loose. Tightening the belt and applying a belt conditioner are the first step to addressing this problem.
You either have a bad or loose pulley, a stretched belt or a tensioner that isn't working right.
The system should have an automatic belt tensioner. If the belt is loose the tensioner must be shot. The tensioner is available from your local auto parts store.
Have the charging system checked. Possibly loose or corroded wiring, a loose alternator belt, or a bad alternator.
Your belt is probably stretched or the tensioner is weak. Try a new belt, or replacing the tensioner. If it is still loose get a 1/2 inch smaller belt.