11.   The disturbances, with overturned cars aflame and the police under attack from flying rocks and bottles, opened a pressure valve in Washington Heights.

12.   The pressure relief valve is a safety feature that is found on most, but not all, hot water heaters.

13.   A pressure equalization valve may need to be replaced by future crews.

14.   An angry Solovyov said the Russian cosmonauts left the pressure valve in the wrong position, according to ITAR-Tass.

15.   Except for a balky pressure valve and two tiny air leaks, the air lock functioned properly during its weekend debut.

16.   The weather was looking up Monday for the liftoff of space shuttle Endeavour, delayed nearly a week by thunderstorms and a leaky pressure valve.

17.   Then a pressure valve had to be replaced, and the launch slipped to Wednesday.

18.   Then a pressure valve had to be replaced, and the launch was moved to Wednesday.