Meet the Sustainability Leader: Encore Cistern – Sustainability Product Innovation

With entries soon closing for edie's revamped 2019 Sustainability Leaders Awards, this new feature series will showcase the achievements of the 2018 winners, revealing their secrets to success. Up next: our 2018 Sustainability Product Innovation winners, Encore Cistern.

Literally, trillions of litres of condensate water are produced – and wasted – each year from air conditioning units installed in buildings across the world. Encore Cistern, a new toilet cistern, aims to change that by utilising this condensate for toilet flushing instead of mains water. Encore Cistern claims to virtually eliminate the need to use mains water – a significant benefit, given that toilet flushing accounts for 43% of total water use in offices.

As Encore Cisterns can used in any building that has air conditioning, they offer the potential to achieve mass water savings on a global scale. Example installations include hotels, offices, apartments, leisure centres and airports. Hotels, in particular, will benefit greatly as they have the highest concentration of toilets in any one building and given their 24/7 operation, are one of the biggest water users in the built environment.

To give an indication of the scale of water savings that could be achieved in the hotel sector alone, the inventors of Encore Cistern – two directors from G&H Group, a building services company – have calculated that the world’s five largest hotel groups have a total of 3,879,991 rooms with toilets, with a further 1,026,282 rooms in the pipeline to be built. All of these have air conditioning installed, potentially resulting in trillions of litres of water a year being drained away. Meanwhile, in the US, data from hotel benchmarking specialist STR shows that 191,832 rooms in 1,477 hotels are currently being built. Installing Encore Cisterns over traditional cisterns would save the average 130-bed US hotel 3.19 million litres of water a year, based on standard 80% occupancy levels. Collectively, across all of these hotels, annual water savings could amount to 4.7 billion litres.

Closer to home in the UK, Encore Cisterns could save the 114 UK hotels currently being built 218 million litres of water a year. The product has been designed to be simple to install or retrofit, requiring the same amount of time and level of skill as conventional toilet cisterns. Instead of the condensate pipe connecting to the waste pipe, it is connected to the Encore Cistern with no disruption to business operations during installation. The system also doesn’t require any specialist maintenance, training or servicing.

According to the inventors of Encore Cistern, no other cistern on the market can store and then discharge a variable amount of condensate to flush the toilet. Conventional cisterns typically only have capacity for 6 litres of water, but the Encore Cistern holds 18 litres – this allows it to store condensate that is fed from the air conditioning unit. Its larger water holding capacity still fits the same tight service voids like a standard model, thanks to a dual chamber design.

To offer worldwide appeal, the bottom chamber of the Encore Cistern is adjustable in half litre increments to hold between 6 and 3.5 litres to meet different international requirements. When flushed, only condensate in the bottom 6-litre chamber empties (compared to conventional cisterns that empty the entire water content when the toilet is flushed).

While flushing, a communication valve opens allowing stored condensate from the top 12-litre chamber to release into the bottom chamber ready for the next flush. The upper chamber continues to be topped up with condensate from the air conditioning unit ensuring a continuous water supply. This means that in hot climates where a huge amount of condensate is generated, mains water should never have to be used. For back up, if there is an unusually high number of flushes in quick succession or the air conditioning is not in use, the Encore Cistern is filled in a conventional way using the mains water supply.

Before the product was brought to market, extensive testing was carried out over a three-year period to establish the amount of condensate generated and how the cistern could utilise it. Further testing was carried out in partnership with Thomas Dudley, an approved Water Regulations Advisory Scheme (WRAS) test centre, and in the construction, architecture and building services sectors to establish potential levels of demand and take-up.

The Encore Cistern was launched in July 2017 and has already received widespread media coverage. Payback claims to be immediate; for new builds and retrofitting refurbishments, it is priced in line with other concealed cisterns of similar quality and can start saving water and money straight away. Another product differentiator of the Encore Cistern is it allows two BREEAM credits and LEED points to be claimed – the inventors say this a first for a toilet cistern.

What the judges said: “The uniqueness and scale of this entry is fantastic. Encore addresses a real system problem within HVAC which has massive potential to drive down water use and is already generating tremendous results.”

edie’s 2019 Sustainability Leaders Award

Now in their 12th year, the RSA-accredited Sustainability Leaders Awards have undergone a major revamp, with a host of new categories and judges, a new Awards venue, and a new Mission Possible theme – making 6 February 2019 the biggest night of the sustainable business calendar.

The entry deadline for the 2019 Sustainability Leaders Awards is Friday, 14 September 2018. The Awards will then take place on the night of 6 February 2019 at the Park Plaza London, Westminster. 


Matt Mace

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