To prevent your tank from leaking, make sure all parts are screwed together properly and the coil is fitted securely. Avoid filling past the maximum line, and check that the O-rings are clean and in place. Using the right coil for your e-liquid also matters, as sub-ohm coils may leak when used with thinner, high-PG e-liquids. Finally, prime your coil by letting it soak in e-liquid before vaping.