It looks like the tank is a version of the CE5 top fill. You can unscrew the top mouthpiece (drip tip) and turn the tank/clearomizer upside down to drain it. You should be able to unscrew the bottom part where you change the coil which will let all the
juice out. I'd recommend not buying a backup for that gear, I'd recommend an "upgrade". iStick 30W and Nautilus Mini. Good luck in your journey.