you mean the thin (copper?) pipe? Here is a fix:

First find out the spot of leak. Go to HD, buy a tube of silicon sealant (about tooth paste size), about $5. Shut water, cover the spot +- 1,2 inch around it, and wrap around it with plastic wrap many many times. Wait at least 12 hours. should last forever. I would probably do something easier, but this pipe is pressured.