How do I fix a leaky vaporizer?

First you need to determine whether the problem is actually a leak rather than a flooded atomizer.

There are generally two ways in which flooding occurs:

1. You've inhaled too forcefully on the cartomizer, causing a large amount of e-liquid to be drawn onto the atomizer. The coil isn't able to vaporize all the e-juice so it either leaks from the tank onto the battery or you're left with a mouthful of e-liquid.
2. Flooding can also occur if you overfill your tank. A distinct gurgling sound will always be present if the problem is flooding rather than a leak.

If neither of the above options seem likely, inspect your tank. You may notice e-liquid seeping from small cracks that will usually be visible at the base of the tank. Certain e-juices can cause plastic tanks to melt or crack when vaped at high temperatures. Unfortunately the only fix is replacing the cartomizer and heating coil (if it's been affected).