Does it take too long for hot water to reach the sink or shower, and have a pleasant, fast bath or uninterrupted use at the kitchen, for dish cleaning? If you have a problem with the slow water delivery, one of the solutions is to install a recirculating pump, a pump that can be easily mounted on a dedicated return cold line. The recirculation is used in both new house developments and as an add-on in retrofit situations, resulting in sufficient and fast hot water supply.
Keep in mind that none of the conventional tank-type or on-demand water heaters can deliver hot water instantaneously; when the recirculating pump is installed, hot water is delivered much faster than without the pump. Depending on the manufacturer and model type, the pump can be factory-built inside the unit (some tankless models) or externally added. One of these tankless models is Rinnai RUR and its Circ-Logic features that work with the dedicated return line or cross over return that uses the thermal by-pass valve. It allows users to customize the system, based on the piping insulation, length of the loop...
The recirculation is recommended mainly for commercial applications and large homes, but it is not worth the effort and money for smaller houses.
The recirculating pump is usually installed on the cold water line either close to the water heater, at the point of use or the furthest point from the unit, so more fixtures can take advantage of the fast hot water delivery.
So, the change on the existing plumbing system includes the dedicated return line from the desired fixture and back to the water heater, covering that fixture with the hot water and any fixtures in between.
Once a decision was made that the recirculation is needed, next is to pick the system;
While comparing the systems, the continuously working system is the last recommended due to its constant work and energy waste when hot water is not in use. It is OK to use it if the system utilizes a smaller pump, as it draws little electricity. A better method is one where the work is temperature- or time-based, where hot water delivery is faster, but water at the beginning is warm, not hot.
According to some reviews, the demand type recirculating system is the best as it utilizes the reliable pump for fast delivery, activated by a switch and when used with the timers, more energy is conserved, as it operates only when demand is high, for example.
One can also go with the indirect water heaters that are equipped with the recirculation port, used for the return line. If the unit is not equipped with such a port, it is recommended to use a T-fitting installed into the drain line.
Either type of the recirculating system is used, the benefits are there; water at the fixture is hot and delivered fast and what is also important hot water stays in the loop eliminating the water waste, energy loss, and inconvenient showers. In addition to the return line installation, it is a good practice to insulate all the hot water lines, therefore, reducing the energy loss significantly.