A scheduled shutdown of a pipeline supplying most of the water for Inland Valley cities has prompted officials to ask customers to limit their water use over a 10-day period. The Metropolitan Water District of Southern California is suspending water deliveries through its Rialto Pipeline from Monday, Dec. 3 to Wednesday, Dec. 12 to conduct scheduled maintenance on a portion of the pipeline, said Kirk Howie, chief administrative officer for Three Valleys Municipal Water District.