Showers are one of the biggest energy guzzlers in the home. But now, the technology to change this has been given the green light. With type approval and the go-ahead from industry bodies for its heat-recovery floor drain, the start-up company Enduce is ready to enter the market.
In Sweden, we are generally good at making properties more energy efficient. Exhaust air is recovered, high-efficiency windows are installed, draughts are sealed and attics are insulated. But there is more to do.
– By far the most power-hungry and energy-consuming household activity, showering, has not been addressed. An average shower uses the same amount of energy as an electric car driving at motorway speed, and we flush that energy down the drain, says Henrik Hagman, founder of the start-up company Enduce.
Energy recovery built into floor drain
His idea of a floor drain that recovers thermal energy during the shower to preheat incoming cold water has been gradually developed since 2008. The patented technology is relatively simple. No pumps, no electronics, no sensors – it is gravity that makes the floor drain work. The aim was to develop a product similar to a standard floor drain, with the major differences being the heat exchanger and integrated energy recovery. According to independent measurements at RISE, the Enduce floor drain offers energy savings of up to 75 per cent compared to a traditional floor drain.
– We want to transform the industry and become what the LED has become to the traditional light bulb. We see that there is no longer any reason to waste large amounts of energy without recycling, says Henrik Hagman.
Enduce received its first major funding from the Swedish Energy Agency in 2021, which later injected a further SEK 3 million to enable further development and commercialisation.
– By the time we contacted RISE 2022, we had already made a large number of iterations to develop a technology that could be type-approved. The number of calculations, documents, registrations and forms you need to complete when developing and launching a new product is beyond anything I could have imagined. Type approval has been the single biggest part, says Henrik Hagman.
We want to transform the industry and become what the LED has become to the traditional light bulb. We see that there is no longer any reason to waste large amounts of energy without recycling.
One product – three categories of building regulations
A type approval is proof that a product complies with the Swedish National Board of Housing, Building and Planning's building regulations. From July 2025, updated rules will apply to "promote new technical solutions and open up the use of new materials and methods". The Swedish National Board of Housing, Building and Planning writes on its website that the previous rules meant that construction was locked into existing solutions.
When the Enduce floor drain had to be tested and approved, the rules had not yet changed. Anders Rosendahl, certification engineer at RISE, explains that the project required unique preparation:
– There is nothing like this on the market, so at an early stage our product certification experts carried out a requirements survey to see which parts of the Swedish National Board of Housing, Building and Planning's building regulations needed to be taken into account when investigating what this product should be tested for. Enduce had to meet the requirements for a floor drain, but also the requirements for a wet room installation product, he says.
– The requirements cover everything from the fact that the heated water must not be allowed to stagnate, as this can lead to bacterial growth, to ensuring that cleaning functions are in place to prevent blockages and leaks.
– There are many aspects that this product both meets and has been tested for, says Anders Rosendahl.
"The people at RISE have been outstanding without exception"
– Developing a technology that works and creates benefits is one thing, but getting it approved by any kind of regulatory system can be a very long journey, as we have seen. My understanding is that the process is designed for innovations to come from established, profitable companies that have three years to introduce a new product. For a start-up company, the product itself is what you are seeking approval for, and it will form the revenue base, so you have to rely on financial support during the process, says Henrik Hagman, who continues:
– Having said that, the people we have had contact with at RISE have without exception been excellent. Benevolent, competent, responsive, objective people who have helped to move this difficult process forward.
Next challenge: Large scale distribution
With type approval and the long-awaited green light from industry organisations such as Säker Vatten, and a place in the FabrikantAccept database required for plumbing and water companies to dare to install the product, the door to large-scale commercialisation has opened.
– Our ambition has been to develop something so affordable that the product becomes available to everyone. It's a bit like the IKEA approach in that we want to offer environmentally friendly, climate-saving technology to everyone, not just the very richest. The next challenge is to make it widely available to the market, scale up quickly, and demonstrate the benefits so that everyone understands, says Henrik Hagman.
How the floor drain works
- In a shower with an Enduce floor drain, the cold water takes an extra 'turn' before it mixes with the hot water (from the domestic hot water tank or district heating centre) in the shower mixer.
Rather than being channelled directly into the mixer as is traditional, the cold water passes through a plate heat exchanger in the floor drain. Here, a large number of metal plates lie next to each other. On one side of these plates, the incoming cold water flows. On the other side, the used, hot shower water flows down the drain. The heat from the used water is conducted through the plates and transferred to the cold water without the two streams of water mixing. - The cold water is heated to around 33°C. This means that less "new" hot water needs to be added to the mixer to achieve a comfortable shower temperature.