PVC fittings used specifically for waste water are sometimes called DWV (drain, waste and vent) fittings. PVC fittings are often white, tan or gray, but green, blue and yellow are also seen. There is no set meaning for these colors, though white and gray are most often seen in plumbing applications, and green is often used for sewage.
Within these general categories, PVC fittings are grouped into schedules or thicknesses. There are many schedules, but the most common are 40, 80 and 120. Schedule 40 PVC fittings are usually white or tan. This size has the greatest inside diameter of the schedules and is often used for carrying cold water. It can only contain liquids with a temperature of 140°F or less. Schedule 80 has a smaller inside diameter than schedule 40 because its walls are thicker.