Some showers and fixtures run cold for a long time before the hot water finally arrives. And this adds up. For example, every 60 seconds of shower run-time amounts to about three gallons of wasted water down the drain. Homes can be designed with plumbing layouts that deliver hot water much more efficiently. DOE’s Zero Energy Ready Home program requires that no more than 0.6 gallons of hot water be discharged from the fixture farthest from the water heater before hot water reaches the tap.