My brother has one of these and the Hydro seems to be a bit of a hit 'n' miss affair. When I first tried it (my first e-cig experince) I was getting something, but not exhaling much vapour at all. My brother of the other hand could make some decent clouds with it. It's down to
vaping technic, long big hard pulls.
However compared to my RN4081 Super Mini, now I've learnt the technique, the Hydro produces a lot less vapour. That could also be due to drier carts, but even when we topped up my bro's Hydro carts and got puffing good the Super mini on a topped cart still bettered it.
Nice looking e-cig, but not sure about the quality (the manual is rubbish). One battery has already died on my bro after just under 3 weeks medium usage. Second battery is now being tempremental. They did arrived uncharged so make sure they're fully charged up before use. And a word of warning, beware of the wadding that holds the juice inside the mouth piece falling out. This has happened twice to my bro out of 15 carts. If you can see the hole whilst looking down into the mouth piece, the wadding has fallen out.
Just my 2 cents or it could be as Mr.Darcy has said, a lemon...