SAN FRANCISCO (KPIX 5) – The people who want us to use less water are part of a system that could be among the biggest water wasters in San Francisco. That system is in hot water, because of hot water.

“After the water is heated up, the condensated water is then discharged into the sewer system,” said Tyrone Jue of the San Francisco Public Utilities Commission. “This is drinking water that is being used for the steam loop.”

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Water is heated to make steam to heat City Hall and 170 other nearby buildings. Although City Hall reuses most of its portion, a quarter million gallons a day goes wasted. Good drinking water ends up in the sewer. It’s a system that is more than 80 years old.

“This system has been set up in the city for many decades, as far as this steam loop. It doesn’t rely on fossil fuels or natural gas to heat these buildings. So in that sense it’s good,” Jue said.

But times have changed. Water is a much more precious commodity now than in the 1930s when steam heat seemed to be a good idea.

The company that runs the heating loop for the 170 buildings, NRG, is looking to start using some non-drinking water from beneath the Powell Street BART station.

“This station has had a problem with water intrusion since it opened in the mid-1970s. And so we’ve been pumping it out and trying to get rid of it since then,” said Taylor Huckaby of BART.

Now 65 million gallons of ground water under BART goes into the sewer each year. The idea is to get that water, not good for drinking, into the heating system to replace the good drinking stuff.

“There is no infrastructure right now to move the water from the Powell Street pumping station,” Huckaby said.

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The company says there are no firm plans and it will be expensive. But in this era of drought, priorities are changing and saving good drinking water is now at the top of the list.

NRG said some of those 170 buildings do use a portion of that water for landscaping and flushing toilets.