A UK-based building services company has launched the world's first cistern to use condensate from air conditioning units to flush the toilet. Called Encore, the environmentally friendly cistern could save 1.5 billion litres of water a year for the 487 European hotels currently being built, not to mention villas, apartments or offices with both toilets and air conditioning.

Encore Technical Director David 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. We've developed the only cistern that uses this free water to flush the toilet.”

UK architects, consultants and specifiers using the new system could also qualify for two extra LEED/BREEAM building sustainability credits.

How it works

The condensate recovery system holds 18 litres of water – three times more than a conventional cistern – but its dual-chamber design means it fits like standard models. The bottom chamber holds six litres, which comes from the mains pipe; the upper 12-litre chamber is filled with air conditioning condensate. When the toilet is flushed, the lower chamber empties then 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 by the mains fed pipe. If the toilet is not used for a period, surplus condensate is fed away. 

Water savings

Compared to traditional cisterns, using Encore would save the average 158-bed European hotel over three million litres of water, based on standard 80 per cent occupancy levels. This means that in total, the new cistern could save them 1.5 billion litres of water a year, filling the equivalent of 600 Olympic swimming pools.