A secondary return pump, also known as a hot water circulation pump, works by continuously circulating hot water from the hot water source (like a cylinder or boiler) through a dedicated return pipe back to the source. This ensures that hot water is readily available at taps quickly, without the user having to wait for cold water in the pipes to run through.
Understanding the Purpose
In a typical hot water system without a return pump, when you turn on a hot tap, you first get the cold water that has been sitting in the pipes since the last use. You have to run the tap for a while for the hot water from the cylinder or boiler to reach the outlet. A secondary return pump eliminates this wait time.
The Circulation Process
- A dedicated return pipe runs from the furthest point of the hot water distribution system back to the hot water cylinder or heat source.
- The secondary return pump is installed on this return pipe, usually near the hot water cylinder.
- The pump pushes the cooled water that has been sitting in the hot water pipework back towards the cylinder.
- Simultaneously, hot water from the cylinder is drawn into the flow pipe to replace the circulating water.
- This creates a continuous loop, keeping hot water moving through the pipes, right up to the tap outlets.
Key Components and Construction
A crucial difference highlighted in the reference is the materials used in the pump's construction:
- Brass Impeller and Pumping Area: The impeller and the area where the pumping action occurs are made of brass.
- Reason for Brass: This is because the pump is constantly moving fresh water. Unlike a heating system pumping treated water (often containing inhibitors), a secondary hot water system circulates potable water. Brass is resistant to corrosion from fresh water, making it suitable for this application and helping to ensure the pump's longevity and the quality of the domestic hot water.
This continuous circulation means that whenever a hot tap is opened, the pipe is already filled with hot water, significantly reducing water wastage and providing convenience.
Benefits of a Secondary Return System
- Instant Hot Water: Reduces the waiting time for hot water at outlets.
- Water Saving: Minimizes the amount of cold water run to waste while waiting for hot water.
- Convenience: Provides immediate access to hot water, especially beneficial in larger properties with long pipe runs.
In summary, a secondary return pump actively circulates hot water through pipework using a dedicated return loop, ensuring rapid hot water delivery. Its internal components, such as the impeller and pumping area, are often made of brass due to the continuous circulation of fresh water.
