Plumbing and water heaters
Compost pile hot tub water heater
...water through a giant compost pile, it was brought from 7 °C to a blistering 62 °C. Not much more needs to be said that the video doesn't say. We love seeing stuff like this, if you come up with your own brilliant backyard inventions or hear of one, by all means tip us off.
Now you know about the compost hot water...