An artist's plan to leave six taps running for a year at secret London locations has angered Thames Water.
The water stunt will use 100m litres
Performance artist Mark McGowan says it is a protest against private control of water in the UK.
The water company has threatened legal action to stop the "irresponsible" stunt which comes during a prolonged drought in southern England.
Last year McGowan left a tap running in a south London gallery, but bowed to pressure to turn it off after a month.
That stunt used 800,000 litres of water, and angered many Thames Water customers and gallery visitors - some of whom turned off the tap themselves.
This time he intends to keep the taps running at secret London addresses, sending an estimated 100 million litres down the drain.
Pull the plug
McGowan said that private water companies made a profit while wasting billions of gallons of water a year through under-investment.
"I understand we are in a drought. But I am an artist so I'm not actually wasting water for nothing."
Mark McGowan's student debt protest
A Thames Water spokesman said the company planned to take immediate legal action once it knew where the taps had been left running.
Pointing out that London and the South East get less rain per head of population than Istanbul and Dallas, he said: "For the sake of the environment we call on Mr McGowan to abandon this childish game now."
McGowan has previously made a name for himself by rolling a monkey nut across London with his nose to highlight student debt, and pulling a bus with his big toe in protest against bus lanes and mayor Ken Livingstone's "ridiculous traffic strategy".