Hotels and other fancy establishments typically have hot water on demand because of their hot water recirculating systems. Once you turn on a faucet, hot water almost instantaneously flows out. Hot water recirculating systems allow hot water to flow constantly in a closed loop. Such systems work well in areas where water is in short supply.
For traditional piping systems, pipe lines terminate at the farthest fixture and users would have to wait for minutes before hot water comes out of a tap. This causes water wastage. For heavy users, the cost of water going down the drain could become prohibitive. A hot water recirculating system eliminates this problem. It can be argued that a recirculating loop can increase electricity consumption; on the other hand, the cost savings one would get from lesser water wastage would offset the energy costs.
In a recirculating loop, a return line is installed from the farthest fixture back to the water heater through the drain valve. The pipes are insulated except for the last 15 feet of the return line to minimize heat loss. The last 15 feet of the return pipe need to be uncovered so that water will be cooled and easily flow back to the heater.
There are basically two types of hot water recirculating systems available: active and passive.
Passive Hot Water Recirculating Systems
Passive hot water recirculating systems are cheaper and more energy efficient than active systems. They cost around $500 to $700, including installation. One passive system sub-type requires the use of a series of small pumps placed in different locations of the piping system. One downside to this particular design is that you need to have an electric outlet at each of the pumps; this type of design can pose a problem with retrofit application.
Another type is the one manufactured by Groundfos, which makes use of a pump installed on the hot water outlet; it pressurizes your hot water system to 3 to 4 psi (pounds per square inch). In this type of design, bypass valves are placed in several locations along the piping line. The bypass valve injects hot water in cold water pipes periodically to ensure that hot water is available to users all the time. The advantage with this set up is that it can be installed even after the sheetrock is up. The downside with this system is that users sometimes notice that cold water coming out of taps are initially a little warm.
Active Hot Water Recirculating Systems
An active hot water recirculating system uses a hot water line that runs throughout the house back to the water heater; a pump also aids it. These types of systems are a bit on the expensive side—costing anywhere from $1,200 to 1,500, including installation. On its own, it can be quite costly to run, with the pump running continuously. It is thus recommended to install a timer for these recirculating systems to minimize or reduce costs.