Every once in a while, I come across a process design that leads to code issues down the road. This usually occurs with small pressure vessels (e.g., less than 5 cubic ft) that fall outside the scope of ASME Section VIII and also fall outside the scope of being a “confined space” (e.g., too small to bodily enter). So the business did not provide a means to isolate the vessel for maintenance or “pressure/leak testing” of the attached piping, which is covered by B31.3. In this article, I will explain the “77% option” that a business can use to pressure-test its piping.