miketrees wrote on Jan 21^st, 2018 at 12:52pm:

I can see it, I have coils of poly pipe out the back hooked up to rain water tank and the water comes out steaming hot after 10 minutes in summer, free hot water, really hot water, to use a still type set up to condense the vapor on a big scale might just work.

You would need a triple–walled clear pipe:

Inner, part filled with water with plenty water vapor above it.
This inner part has two walls, inner one does not go to the top and water is not filled over the level of the inner wall.

Final outer wall gets cold water from out the ground running from the top, down the sides of the pipe, cooling the vapor and condensing it. condensed water runs down the wall of the pipe between the inner and centre wall and is collected and used.

I would elaborate that, have the cold water instead running in a coil in the water vapor part, in at the top out at the bottom.

Condensing, cooling is done with counterflow: hot vapor heads down, cooling water heads up.

In the shop a bloke came in wanting a new still: his didn’t work well. We were delighted to sell him an expensive still taking his still as trade in. His condenser was connected the wrong way round. We fixed that and sold his still for a near-new price. So work in counterflow, will really boost your system’s efficiency.