Ashley Prescott of Power-Pipe discusses how waste water heat recovery can stop you throwing money down the drain every time you shower
In terms of the practicalities, waste water heat recovery (WWHR) couldn’t be more straightforward. A WWHR system is essentially a length of copper piping which works by recovering heat from outgoing shower waste water and using this to pre-heat incoming cold shower water. This helps to save energy, lower hot water bills and also to cut down CO2 emissions.
By recycling heat energy in this way, you not only increase the amount of available hot water in a home, you also reduce the load on its heating system.
Why install it?
Wasted hot water is a huge untapped resource in UK housing. That’s why it is important to have a good understanding of technologies like WWHR which can make showering and other hot water processes more energy efficient.
Believe it or not, a shower uses more energy than any other appliance in the home. To put that into perspective, the average UK shower lasts eight minutes and uses the same amount of energy as:
- boiling a kettle 22 times
- leaving the TV turned on for 26 hours
- running a laptop for 36 hours
- having an LED light on for 13 days.
Up to 90 per cent of heat produced during showering is lost down the drain but most of it is recoverable through installing a WWHR system.
The bottom line is that WWHR systems can be up to 70 per cent efficient and are compatible with all types of heating systems.
What are the cost-savings self-builders can expect?
Put simply, installing a WWHR system can save up to 10 per cent a year on annual energy bills or 500 Kwh per person.
In a typical household, this could be a cost saving of £80 to £100 a year, and the more people using the shower, the greater the energy saving returns.
As well as cost savings, waste water heat recovery also reduces annual carbon emissions by between 300 kg and 1000 kg. This obviously depends on how long people spend in the shower and what fuel they use to heat their water. These systems have no moving parts or components. You don’t need to switch them on or off. So once fitted, it’s job done as they require no maintenance or user interaction.
Also, if they are made entirely from copper, they are expected to last the life-span of the building and will continually save energy every time the shower is in use.
Is it a good way to help meet Building Regulations?
If you are building a new home, WWHR is a no-brainer. Not only will it save energy and reduce your carbon footprint, it could also keep building costs down.
Believe it or not, it is the most cost- effective way of increasing a Standard Assessment Procedure (SAP) score – required to pass Building Regulations – something you will have to familiarise yourself with if you are building your own home.
Dependant on the model or size, these systems can cost between £250 to £750 to buy and install but can offer a generous SAP uplift in the region of two to 12 per cent. This is the equivalent energy saving to triple glazing or solar thermal, but at a fraction of the cost. It could also be the difference you need to achieve compliance on a home – without breaking the bank.
Return on investment is typically around five to six years based upon an occupancy of four people.
How do you install WWHR?
Installation is normally undertaken by a professional plumbing or mechanical contractor and takes less than an hour to complete.
If it is going into a new home, the process is straightforward as these systems come with specialist design or commissioning. If you choose a 110 mm diameter model, it’s even simpler, as it replaces a section of the soil stack.
If the WWHR comes with 22 mm connections, this again means less work is required by the installer. This is because there is no need to reduce the size of the incoming mains water feed (also 22 mm) which would restrict the flow of the water passing through it.
When choosing a WWHR system, we would always advise you to opt for a model which has a twin wall between the waste and potable water. This helps to avoid any possible cross contamination between the water supplies and will also allow for a leak to be detected if one occurs.
How do you set it up?
There are three ways to set up a waste water heat recovery system. The most effective way is according to the System A configuration where the pre-warmed water from the WWHR unit is connected to the shower and the water heater. This provides maximum performance and energy savings.
In some cases, where the System A configuration is not possible, it may be necessary to install according to System B (pre-heated water to shower only) or System C (pre-heated water to water heater only), however this will reduce efficiency performance.
Is it worth retrofitting?
Retrofitting is more complicated as it is usually difficult to access the pipework of a building. That said, we have worked with self-builders who have successfully done this and have case studies on our website for anyone looking to do it.
Is there anything else I need to know?
Other design requirements you need to consider with WWHR include:
- it needs to be installed vertically and inside the building;
- it must be fitted on the floor below the shower – this is why it can’t be used in a bungalow or ground floor flat;
- WWHR is compatible with all water heaters but will not provide any savings if used with electric showers. This is because electric showers cannot regulate both temperature and flow rate.
Ashley Prescott is UK director at Power-Pipe