热水循环系统使用水泵将热水从热水器循环到水龙头，将等待热水的时间几乎缩短为零。所有热水循环系统节约用水。但并不是所有的系统都能节能;有些系统实际上会导致更高的能源账单。选择按需系统。有三种类型的热水循环系统:热虹吸系统、时间和温度系统和按需系统。按需供水系统在绿色家居中最有意义，因为只有在需要的时候，热水才会被泵到使用点，最大限度地减少了待机损耗。它们被手动或无线遥控或运动探测器激活。这种系统是廉价的添加时，管道是粗糙的，并可以负担得起的加装到现有的管道系统。作为一种改进安装，按需系统使用现有的冷水管道作为返回，借助于一个特殊的阀门。 Time and temperature systems. Hot water is circulated automatically to anticipate demand with the help of a timer and thermostat. An override allows homeowners to activate the pump at non-scheduled times. While time and temperature systems cut waiting time, they increase standby heat losses. Hot water lines are essentially turned into extensions of the hot water storage tank. They save water but increase net energy use. Thermosyphon systems. These work only in a home with a tank-type water heater located below the hot water taps — for example, in a basement. A continuous piping loop is installed between the water heater and the fixtures, with a return line coming back to the heater after the farthest fixture is served. Because the returning water is cooler than the water in the top of the water heater, a thermosyphon…