there is a one way valve in the hose from your vacuum source to you BRAKE BOOSTER. There should only be brake lines going into your master cylinder.
With out the valve you with have no vacuum assist for your brakes. They'll work but you'll need to push them pretty hard.
Unless you've changed the brake booster you should be able to use the original hose with the valve in it. If the hose bends the wrong way you can use the same size hose and just put the original valve in that line.