What is a WWHR and how does it work?

Usually, a WWHR (Waste Water Heat Recovery) system works by taking the heat from the water your shower or bath sends down the drain. This waste heat is used to warm up the incoming cold mains water, thereby reducing the load on your boiler. It therefore reduces the energy required to heat your water up to temperature. A typical WWHR system might look like a long vertical copper pipe, designed to act like a heat exchanger, where the warm water runs alongside the colder mains water. Some of the latest models are more compact, which is more ideal for a retro-fit, where inserting a long copper pipe to the waste water system might not be ideal, or possible.

WWHR system are typically about 60% efficient, so they convert 60% of the potential energy in the waste water back into heat for the incoming water. This can save you money on your bills, especially if you use a lot of hot water in your home. The payback period will vary, depending on varying factors.

A simple device, a WWHR system has no electrical components, no pumps or controllers and as such, requires very little maintenance. They have an expected lifespan in excess of of 20 years. In domestic properties, they have been seen in the past as expensive, with a long pay-back period, though recent developments in the technology have changed this.

Retrofitting a WWHR system

In most cases retrofitting is possible, but this depends on the location and the usual building fabric restrictions. The length of some of the earlier devices meant that most showers or baths weren’t suitable for retrofit, but new compact designs have changed this. It is much easier to get one installed when you are fitting a new bathroom, or designing your self-build project of course.

Are they worth it?

Until 2015, installers often used WWHR systems as a means to get a new home up to Sustainable Homes Code standards, rather than for their money saving benefits. Now that the Sustainable Homes Code is no longer around, although you certainly will save some cash with a WWHRS, the payback period will depend on varying factors. A typical saving on an average home might be £20-30 a year, meaning the payback time would be around 40 years. That being said, if you have high demand and use a lot of hot water, it will look more attractive.

For more information or an idea of how feasible a WWHR system might be for your project, please get in touch.

Leave a Reply

Your email address will not be published. Required fields are marked *