I've found that it can leak if the bottom of the cotton wick is long enough to interfere with the o-ring that's right below the wicking channel. If the cotton sits on that o-ring it seems to weep a little from right above the airflow control ring. I wish the wick cutout was just a little less deep. It's right on top of that o-ring. You can see the o-ring right below the excellent wicking job in the bottom right image here (with rayon).
As others have said, it's much easier to get enough cotton in the channel if you use a large diameter coil. I use a 3mm rod for SS Clapton coils (they spring out a bit further than 3mm) and a 3.5mm rod with 26-24g SS, wicked with cotton.
Using larger coils to get lots of cotton and making sure the cotton doesn't touch the o-ring has made this tank fairly trustworthy for me. Rayon may have different rules. With 70VG juice I only keep the juice control ¼ open. This is still a new tank for me, so I have lots more to learn. Just thought I'd post my experiences so far.
As others have said, it's much easier to get enough cotton in the channel if you use a large diameter coil. I use a 3mm rod for SS Clapton coils (they spring out a bit further than 3mm) and a 3.5mm rod with 26-24g SS, wicked with cotton.
Using larger coils to get lots of cotton and making sure the cotton doesn't touch the o-ring has made this tank fairly trustworthy for me. Rayon may have different rules. With 70VG juice I only keep the juice control ¼ open. This is still a new tank for me, so I have lots more to learn. Just thought I'd post my experiences so far.