Interpretation #8378

3" PVC 1/4 bends are permitted to be used at the base of a stack (vertical to horizontal.) Drainage fitting nomenclature and geometry are regulated by the referenced fitting standards. In the case of PVC drainage fittings, that standard is ASTM D3311. Quoting from the IPC Commentary, "a fitting of one material will not necessarily be identical to a fitting of another material with the same name. For plastic drainage piping materials, a quarter bend fitting is considered to be "flow equivalent" to a short sweep pattern even though they do not have identical pattern dimensions. This is because the interior of those fittings are much smoother than for cast-iron fittings." It is important, however, not to confuse a "1/4 bend" with a "1/4 bend vent." IPC Commentary Figure 706.3(4) shows the difference.