If hot water sits in a pipe for more than an hour or so, it will lose much of its heat no matter how well the pipe is insulated. When you start your shower, you’ll notice this cold or tepid water coming out before the warm water. This wastes tremendous amount of water and energy.
Recirculating water systems use a variety of technology to assure you that very little cold or tepid water comes out of your tap when you turn on the hot water or warm water. Typically, there may be a loop of hot water flowing through your home either continuously or only upon demand activated by an occupant sensor, switch, or a person attempting to draw hot water from the tap. With these recirculation systems, you get hot water almost instantly when you turn on the tap for hot or warm water. With little delay, there is little wasted water.