These valves use a screw type valve instead of a simple flap, and they have a pressure regulating mechanism that will vent water to the ground if the intake pressure exceeds a set level.

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High demand for water amid the heat wave and problems with soil shrinking as the ground warms has resulted in burst pipes and low water pressure in Oklahoma City, prompting officials to issue mandatory water-use restrictions for the first time in at least a decade, according to utilities department spokeswoman Debbie Ragan.

CNN: Heat advisories issued to states dwindles to 15

The superintendent of the Pecos Valley Artesian Conservancy District, Dennis Karnes, can still remember sitting on a well-pipe as a boy and being launched into the duckpond as soon as the farmer opened the valve and natural pressure spewed several thousand gallons a minute of ground water against his legs.

ECONOMIST: The Pecos river

It extracts oil from the ground using a method called fracking - pumping down a mixture of sand, water and chemicals at high pressure.

BBC: US to become 'world's biggest oil producer'