Waste Water Heat Recovery (WWHRS) is a system or technology that uses the residual heat from waste shower water to preheat the incoming cold feed that refills the system.
Therefore, less energy is required to heat that water to the required temperature. WWHRS saves energy, what would be wasted heat energy going down the drain is recovered and reused.
As properties become more efficient preventing energy loss in fabric and heating, hot water energy will become the largest source of wasted energy in a property.
How WWHRS Works
The main requirement for WWHRS is the incorporation of a Thermostatic Mixing Valve (TMV) on the shower mixer. As the cold mains water starts to preheat from the WWHRS heat exchange the TMV will automatically reduce the showers demand of hot water from the properties water heater. If preheated water is also being sent to the water heater, then less energy is also required to heat the preheated water to the required temperature.
Waste Water Heat Recovery (WWHRS) can be used alongside any method for heating shower water.
- Combi Boiler (All fuel types)
- Hot Water Cylinder
- Thermal Store
- Heat Interface Unit (HIU)
- Heat Pumps
As showers will always require a hot water source, WWHRS can always be incorporated to save energy by sending pre-heated water directly back to the cold side of the shower. Some heating types and some property configurations may not allow the preheated water to be sent back to the water heater as well.
There are three installation methods to choose from, each having an effect on the WWHRS performance and efficiency.
● System A, the most efficient, preheated water is supplied to the water heater and the shower.
● System B provides preheated water to just the shower. Lower WWHRS efficiencies produced than System A or C, but it is the easiest method to install or retrofit.
● System C provides preheated water to just the water heater. Greater WWHRS efficiencies than System B are produced but lower than with System A. This installation method is often used when two showers are running into one WWHRS.
Benefits of WWHRS
- Horizontal and vertical options catering for all application types and locations
High-efficiency units recovering a large proportion of wasted shower energy
Easy to install
Cost-effective solution, ROI typically within one to four years of use
No end-user interaction is required
Double-walled heat exchangers
KIWA validated efficiencies of up to 68.5%
Legionella control risk assessed
SAP listed on the Product Characteristics Database (PCDB)
There are horizontal and vertical WWHRS product types. The suitable application of a horizontal or vertical product is determined by the building type, the location of the shower within the building and the showering environment.
The Recoup Pipe HEX is an example of a vertical WWHRS product type. It is designed to install on a lower floor under the location of the shower. Therefore, it is only applicable to showers on the first floor and above. The Recoup Easyfit+, Recoup Drain+ Range, and Recoup Tray+ are examples of horizontal WWHRS product types. The Easyfit+ is specifically designed to install under a bath or raised shower tray. The Drain+ Range has wet room applications. The Tray+ incorporates the heat exchanger into a shower tray itself. Horizontal WWHRS products are typically installed on the same floor as the shower and therefore can be applied to ground floor showers as well.