Don Arnold has devoted most of his career to plumbing products,with roles ranging from designing, marketing, writing and training. He has been a contributor to Supply House Times for more than 20 years. He is the author of College of Product Knowledge, the product training course introduced by Supply House Times in 1979, which recently was updated and released in a CD format.  Don Arnold can be reached at INTERSOURCE, 646 Williams Ct., Gurnee, IL 60031, 847/918-7015; or e-mail: donarnold@earthlink.net.