Advisory expert systems can be effective aids to efficient water treatment plant operation. Expert systems have been defined as computer programs incorporating judgement, rules of thumb, intuition, and other expertise to provide knowledgeable advice about a variety of tasks. An expert system designed to aid operators of smaller water treatment plants is being developed. The system will both diagnose common problems associated with the operation of water treatment plants and explain the underlying causes of these problems through a tutorial component. This paper describes the development of the tutorial component.