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Huge water-saving potential for cistern that re-uses AC condensate

Two directors from M&E contractor G&H have created Encore, the world’s first cistern to use condensate from air conditioning units to flush the toilet.

Graham Kelly and David Davis estimate their invention, by re-using the waste water could save a hotel almost two million litres a year based on standard 80% occupancy levels.

The water savings will be even higher in hotter climates where more condensate is generated – for instance, it could save 2.4 billion litres in the 302 hotels currently being built in the Middle East.

They say that it will also allow those specifying to secure two extra BREEAM credits and LEED points – a first for a cistern design.

Mr Davis said: “For decades we’ve designed and installed schemes and watched the stream of water produced by air conditioning units literally go down the drain. When you consider how many buildings use air conditioning across the world, billions of litres of condensate water is generated - all of which has been wasted, until now.

He added that earning BREEAM credits was a distinct benefit. He said:

“Responsible businesses striving to construct the greenest buildings know BREEAM credits and LEED points are very hard to come by. Gaining two for choosing an Encore cistern is simple and a great advantage.”

The patented technology means the amount of water used in each flush is adjustable, from six litres to 1.5 litres, to meet different international requirements.

How it works

Encore holds 18 litres of water, three times more than a conventional cistern, but its dual-chamber design means it still fits like standard models.

The bottom chamber holds six litres, which is fed from the mains water pipe, while the upper 12 litre chamber is filled with air conditioning condensate directly from the AC system. When the toilet is flushed, the lower chamber empties and refills with condensate from the upper chamber.

If there are multiple flushes close together or the air conditioning is not in use, the cistern is filled in the conventional way from the mains-fed pipe. If the toilet is not used for a period of time, any surplus condensate is fed away to the drain.

Mr Davis said: “All buildings need toilets so why wouldn’t you use a cistern that recycles a free, sustainable water source and immediately saves money especially when there is a global water shortage crisis?”

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