What should be the slope for a horizontal drain pipe?

The requirement for a horizontal drain pipe is to have a slope of 1/4 inch per foot. This slope is crucial for ensuring proper drainage and preventing the accumulation of waste and water in the pipe. When the slope is set at 1/4 inch per foot, it facilitates the flow of wastewater through the pipe by utilizing gravity to do so. This recommendation helps to maintain effective drainage, reduces the likelihood of clogs, and ensures that the system operates efficiently.

Other sloping options would not promote the same level of efficiency. A slope of 1/8 inch per foot is considered too gentle and may lead to poor drainage performance, while steeper slopes like 1/2 inch or 3/4 inch per foot could potentially cause issues with waste moving too quickly, not allowing debris to settle properly, which can also lead to clogs. Therefore, the established standard of 1/4 inch per foot is the best balance for effective drainage in plumbing systems.