The best one made, but made no longer, was produced in Bellingham, WA. A
simple still and condensor system with fitting to attach to a pressure
cooker. The coil, exiting from the center made every increasing circles and
ended up pointing down into the receiving unit (glass, cup, what have you),
The twist was a series of square fins slid over the coil. Each one had a
die punched hole in the center which caused a slight turn so as to follow
the coil. This die punched center also allowed a metal to metal fit with
the coil that encourage the transfer of heat energy from steam to coil
tubing wall to fins. A nice flow of air over the 16-18" diamerter by 4"
high saucer shaped device increased efficiency. Using the pressure cooker
increased time needed and efficiency as well. For a small amount of fuel
one could produce 1 gallon of water per hour. Water was pure too! Never
could figure out why they went of production and business. Maybe Ole Thom
can track it down since he's from that area? Anyway I had mine made from
scratch and included the pressure cooker device in the coupling that keeps
it closed until a certain temperature state is reached; i.e. evaporation.
If it cools the device closes. Haven't reached one gallon per hour but
nearer 3/4 gallon. Neat thing is when it starts working efficiently the end
flow is almost a steady stream not the expected dripdrip drip etc.

MST