Whether getting a mini-tummy tuck or complete tummy tuck you will likely have drains. When I perform mini-tummy tucks I usually use one drain, and two drains in a complete tummy tuck. The drains help remove excess fluid throughout the healing process.
A natural part of the healing process includes your body producing a little fluid. Your body is also able to reabsorb some fluid, but in the beginning there is more than your body can handle. The drains help remove that fluid. In most cases, the first drain (when two are used) can be removed in about one week. The second drain is usually removed between the first and second week. The same 1-2 week period applies when only one drain is placed. If there is more fluid than average draining into the drains they may need to stay longer. The important thing is that they are removed when your body is able to handle things on its own.
I hope this info helps!
Web reference: http://www.dr-rubinstein.com/abdominoplasty.html