Wastewater Heat Recovery System


Thankfully, as a country we are becoming more and more environmentally conscious. As we know, it is critical to protect the environment so as to reduce the destruction of eco-systems. It is more of a moral obligation for humans to protect the environment from pollution and other activities that lead to environmental degradation.

Excitingly, lots of manufacturers now produce approved equipment that effectively recovers heat from your hot water before it runs away down your drain. This saves us both energy and money – a winning combination. None of us want to waste money. Certainly, most of us do not want to waste energy and will look for ways to be ‘greener’ wherever possible. When we take a bath or shower or use appliances such as dishwashers or washing machines, the hot water waste simple goes down our drain.

How does the system work?

A heat exchanger pipe is used inside the the waste water pipe. The heat eaxchanger pipe has cold water running through it. This could be installed under the shower tray, for example. Inside the heat exchanger pipe, the cold water will collect some of the heat from the waste warm water. This warmed up water then takes less energy to heat than it would had it been heated from cold. Your preheated water can be sent to your hot water cylinder, or it can be sent directly to the cold water feed on your mixer tap.

The devices are typically around 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.

If your system is being used for bath water or for your washing machine or dishwasher, the process is a little different. In this instance, a storage vessel is required to hold the the warm water until the cold water runs through it to collect the heat. Though these systems can be less efficient than the exchanger pipe system, it will still have an impact. Unfortunately, they can often take up a bit of room (storing the waste water) too.

How is it installed?

Most wastewater heat recovery (WWHR) units are about 80mm thick, one metre long and simply look like thick pipes. Suiting an upstairs bathroom, they plumb in vertically. Alternatively, Showersave produce horizontal units which are suited to ground floor showers as they sit inside the shower tray and capture the warm water as it enters the drain. Installing a WWHR in your shower is a great place to start as the you generally have a pretty consistent stream of waste warm water.

What’s the cost?

At a cost of upwards of around £400 plus installation costs, they’re not the cheapest bits of kit. However, these systems have no running maintenance costs. The impact on your energy bill won’t be gigantic, however, the impact using less energy will have on our environment is important. In an average household, you could expect to save around £20-30 a year on your energy bill. Of course, if you use a lot of hot water, it can begin to look a lot more attractive. For hotels or other businesses that use an awful lot of hot water, it could be a great investment too.

Is it worth retrofitting one of these?

If you are not building a new extension or self-build and not renovating your bathroom or kitchen, is it worth retrofitting this equipment in your home anyway? In some cases retrofitting may be possible, but the bulk and length of the recovery device means that most showers or baths wouldn’t be suitable. It is much easier to get it installed when you are fitting a new bathroom.

Interesting fact: Most people believe having a shower is more energy efficient than having a bath. However, an eight minute power shower uses 136 litres of water, whereas the average bath uses just 80 litres in comparison. 

The Team @ Acre Design hope we have given you some food for thought! Please check out or latest projects if you’d like to see more of what we’re made of. Our InstagramPinterest and Facebook pages are all brimming with extension, loft conversion and self-build inspiration too!

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