What Does a Hot Water Recirculation Pump Do in a Closed Loop Water System?

Since ancient times, the delivery of potable hot water within a household has been one of the most desired conveniences of daily life. But the delivery of hot water has always remained a much bigger challenge than that of cool water. The increased temperature and pressure of hot water, the costs of heating it, and the waste of water and energy once its heat dissipates is a constant set of problems that we wrestle with still today. The combination of a closed loop system with a hot water circulation pump solves a lot of those ancient problems and addresses some modern-day challenges.

The loop circulation system carries, or loops, fresh water throughout the house or building. An open loop system uses the same pipes to carry both hot and cold water throughout the house and is generally not found in modern-era construction and remodeling. In these systems, hot water comes from a boiler or water heater and is circulated throughout the building by a central heating pump. Most codes for new construction require the use of a closed loop system. Closed loop systems conserve energy and water, and often use recirculation pumps, valves, and vents to control pressure, temperature, and direction.

Closed loops are essentially a hot water recirculating system that conserves both energy and water. Energy is required to heat water, and too many branches of piping in the delivery system for hot water will have a cooling effect on the water as the heat dissipates through the pipes. A closed loop system limits the number and length of such branches. A hot-water recirculation system saves water and utility costs as well as energy and sewer expenses. It also helps reduce the shortage of fresh water in many areas. And a closed loop system provides the nifty side benefit of delivering hot water to your chosen tap immediately, without making you wait for the water flow to “warm up.”

Picture a looped system dedicated to the circulation of hot water that begins at the water heater. It carries the hot water in one direction with the help of a check valve installed on the supply line to prevent backflow. The heated water stops at each tap (baths, kitchen, laundry, etc.) but does not branch off nor deviate far from the taps. It does not share any pipe with cold water (the cold water has its own separate loop). As the hot water that is not tapped completes its run through the system, a dedicated hot water return line brings it to the hot water recirculation pump which pushes it to the water heater for reheating and recirculation. Since the same water is recirculated, it is still at least somewhat warm when it returns to the water heater, and less energy is used to heat it again.

Unlike an open loop system, the dedicated return line of a closed loop system prevents the possibility of warm and cold spots becoming mixed and lowering the temperature of the untapped hot water. It also solves the wasteful problem of dumping lukewarm water down the drain by bypassing it into the cold water line.

A closed loop hot water water circulation system does not rely on gravity to circulate the water, yet there must be some force acting on the water to get it back to the water heater in order to close the recirculation loop. To do that, a specialized type of centrifugal pump, called a hot water recirculation pump or hot water circulator pump, is placed on the hot water return pipe at or near the water heater. Hot water recirculating pumps are specially manufactured to handle a constant flow of heated water. They are built with specialized housings, coatings, and internal components that can withstand the harsh effects of constant heat. Be sure that the pump you choose for this purpose is intended for potable water applications (drinking and cooking) and is also compliant with the Safe Water Drinking Act requirements for low lead in potable water applications.

As you shop for hot water recirculating pumps and other water system components, be aware of whether you have a hot-water tank or a tankless water heating system. It would also be helpful to know whether your water circulation system consists of one pipe for hot and cold water, or includes a dedicated return line for hot water. Lastly, remember that Zoro supplies pipe insulators, circulation pump timers, electronic timers, and water heater thermostats to help you save even more on energy costs. Be sure to consult a professional before you begin any such work on your water system.

The product statements contained in this guide are intended for general informational purposes only. Such product statements do not constitute a product recommendation or representation as to the appropriateness, accuracy, completeness, correctness or currentness of the information provided. Information provided in this guide does not replace the use by you of any manufacturer instructions, technical product manual, or other professional resource or adviser available to you. Always read, understand and follow all manufacturer instructions.