Heat Recovery. By recovering heat from household wastewater, the Power-Pipe can reduce water-heating expenses by up to 40 percent, the maker says. It consists of a section of drainpipe with a wrap of supply tubing. The pipe connects to the drain line with hubless clamps, and the wraparound tubing gets fed into the supply side of the water heater. A 5-foot section of 3-inch pipe costs $630. RenewAbility, 877/606-5559, renewability.com.