Usually, atomizers with a bottom coil suffer from leaks. Whilst not using the e-cigarette, you should store a bottom coil atomizer upside down to keep the liquid from getting out. Atomizers with bottom coil leak, if they are stored at colder temperatures and then introduced to room temperature. Warmer environment causes the liquid to expand which might lead to leaks. The second reason is that the liquid level is too low which causes the loss of vacuum in the atomizer. The liquid level in the tank should be kept above 1/3. The third reason is that there could be a crack in the glass/plastic parts of the atomizer. This allows extra air to access the atomizer causing the loss of vacuum. In this case, the glass should be replaced.