Neat idea. “What I have made is a compost heater, inside a wheelie bin with 20 mm poly pipe coiled around the outside wall of a pipe – about 8 metres in each bin.” he says. “A few years ago I helped build a large compost heap that had about 300 meters of 25mm rural pipe going through it. After 4 weeks this system was providing enough hot water for 35 people to wash up and shower with. I was there for 3 months and we kept adding compost onto the heap and it worked the whole time I was there.