Some ingenious individuals have come across a solution to patch this “open hole in the wall” problem and recover this wasted heat instead of trying to address it with expensive and high maintenance/complicated water heating systems. The solution is quite simple, use a heat exchanger (drain water heat recovery DWHR) to capture that wasted heat and use it to preheat the incoming cold water. The technology is relatively affordable and straightforward. Best of all, it requires no maintenance and has a 50+ year life expectancy. It is also 100% recyclable because it is 100% copper. The longer, more efficient drain water heat recovery units will capture 59% of the wasted energy. That means incoming cold water at 50 °F (10 °C) is preheated using the waste energy from outgoing hot water from a shower to 80 °F (27 °C).