Ralph McDonnell, 59, partner in Westmark Enterprises, a manufacturers representative agency based in Southern California, died March 31 of cancer. McDonnell began his plumbing distribution career in 1968 with Pioneer Plumbing Supply in Phoenix, Ariz. In 1976 he was hired as the national sales manager for Rapid Fit Enterprises. McDonnell and Roger Peterson formed Westmark Enterprises in 1982. Today the company has more than 50 employees and a 130,000-sq.-ft. facility, serving Southern California, Arizona, southern Nevada, and Hawaii. “He gave so much and asked for so little,” said one of his two daughters.