The world’s first cistern to use condensate from air conditioning units to flush the toilet has been launched and would save 4.7 billion liters of water a year for the 1,477 US hotels currently being built.

“For decades we’ve designed and installed schemes and watched the stream of water produced by air conditioning units literally go down the drain but not via the toilet,” says David Davis, director of UK-based company Encore (pictured above). The new, environmentally friendly, cistern developed by Davis’ company uses a free, sustainable water supply that has previously been drained to waste.

The cistern is suitable for villas, apartments, offices – almost anywhere toilets and air conditioning are found together. And in another first for cisterns, Encore allows architects, consultants and specifiers to secure two extra LEED points – the US Green Building Council’s gauge for sustainability.

“Air conditioning units have a pipe that drains all the condensate away,” says Davis. “We developed the only cistern that uses this free water to flush a toilet. When you consider how many buildings use air conditioning globally, billions of liters of condensate water is generated – all of which has been wasted – until now.

All buildings need toilets so why wouldn’t you use a cistern that recycles a free, sustainable water source especially when there is a global water shortage crisis?

Water savings 

Data from hotel specialist STR Global shows 191,832 rooms in 1,477 hotels are currently being built in the US. Compared to traditional cisterns, using Encore’s new cistern would save the average 130-bed US hotel 3.19m liters based on standard 80% occupancy levels. In total, Encore would save them 4.7 billion liters of water a year, filling the equivalent of 1,880 Olympic swimming pools.

How it works 

Encore holds 18-liters of water – three times more than a conventional cistern but its dual-chamber design means it fits like standard models. The bottom chamber holds 6-liters, which comes from the mains pipe.  The upper 12-liter 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.

“Responsible businesses striving to construct the greenest buildings know how hard it can be to get LEED points,” says Davis. “Gaining two points for flushing with an Encore cistern makes it simple.”