WWHR: What is Waste Water Heat Recovery?

Sean Mills
I often recommend Waste Water Heat Recovery (WWHR) units for SAP calculations, but still find that unlike solar panels or other technologies, many people are unaware of what this technology is or how it works. So what is WWHR?

 

A WWHR unit is a system designed to retrieve thermal energy from hot water used in a shower before it disappears down the drain. This happens through a heat exchanger, in which cold mains water is passed around a copper waste pipe to gain a temperature rise, before continuing to the boiler ‘pre heated’. This in turn relieves the workload of the boiler.

 WWHR

How a WWHR system works (click to expand)

The benefits of this system to the carbon output of a home or commercial unit can be significant, and can often improve a SAP score by around 6%. As a system with no moving parts or maintenance routine a WWHR unit can be considered a ‘fit and forget’ solution to carbon requirements from SAP, CfSH or BREEAM. Most models resemble a length of copper piping and so can be fitted behind the scenes with little additional considerations by the builder or occupant.

So what about cost? The most popular models from Showersave such as the Recoh-vert RV-3 cost around £400 to install, which compared to much larger potential outlays for solar panels makes WWHR an attractive prospect for those looking to save carbon. Some estimates suggest that there is already a WWHR unit in 20% of new homes.