Engineering design decisions are multifaceted, often based on a balance of probabilities or advantage. Recent regulatory changes in the U.K., reducing water closet flush volume and introducing a wider range of flushing mechanisms from the international marketplace provide an opportunity to identify some of the factors that inform such a decision-making process, namely a consideration of the system implications of any decision, a recognition of the limits imposed on system or appliance operation and the exercise of choice.
The design of building services is all about systems and the way they operate to meet user demand. The operational characteristics of each constituent component must be compatible to ensure user satisfaction and compliance with operational standards, whether safety-based or driven by economic factors. The "systems" approach to design, an overused term, describes the approach required from system designers, component manufacturers and code authorities.