I like my protanks. I have 5 of them. They leak out of the bottoms of the 510 connection. They also can leak out of the mouth piece when you remove the base to refill. Only the liquid that is trapped in the center post. If the temperature is hot and your tank gets hot, it will flood and leak. The best thing I have found to deal with this is to stick a que tip in the mouth piece before you unscrew the base to refill, clean or whatever. And keep a spare napkin handy.
Also, like I said, it will flood on you eventually. And when it does, you need to remove the base and atty to clean it. Wipe out all the flooded juice beneath the atty, reassemble and your back in business. On a hot day, you can expect to do this a few times.
And if anyone tells you otherwise, it's BS. I own 5 of them. I work outside in the heat. I've put brand new atty's in, tried thinner, thicker juices and no matter what, they will leak. I have owned them for a few months now. However, I think they or worth it.