Delaware Code
Chapter 79. BASIC PLUMBING PRINCIPLES
§ 7922. Roof terminals, soil or waste stacks.

The soil stack shall extend full size upward through the roof and have a free opening, the roof terminal being so located that there will be no danger of air passing from it to any window and no danger of clogging of the pipe by the frost or by articles being thrown into it or of roof water draining into it.