I find that a full inch of water over the bottom of the stem is enough, but some people like a little more for that rumbling smoke
Here are a few things to try
The present study addresses these limitations through a cumulative meta-analysis, quantifying dose-response relationships across various exposure types including active smoking, SHS, and e-cigarette use
Every part of the tobacco sector harms the environment, from the huge amount of firewood needed to cure tobacco leaves to non-biodegradable butts that leak poisonous chemicals into water tables, soil and the food chain
Siberia delivers all of that in a format that fits completely into daily life
Cartledge, Paul (April 2, 2007)