Yes, you're right about screwing it down. Most of the time the golden rule with everything vape related is just slightly hand tighten it but with these heads you have to screw them down tightly so that the drip tip can also screw all the way down and make a good air lock. I used to get a slight bit of leaking / bubbling but I soon discovered that if they're filled to about 2.8ml (just underneath the bottom of the top coil) that they're fine. Over the last couple of years I've tried just about everything and for simplicity and price I just love them. Being dual coil you never get a dry burn and the flavour is much more intense but of course as you'll know, the down side is that they suck up juice like an Ethiopian elephant at a watering hole. Like I say, give it a couple of months and there'll no doubt be the 'new' 30 with replaceable tips anyway. Happy vaping, Jase.