Why are screw-type drainage fittings preferred over straight threaded fittings for urinal drains?

Screw-type drainage fittings are preferred for urinal drains mainly due to the specific design of their inlets, which are strategically tapped with a pitch of 1/4 inch per foot. This particular pitch is essential because it ensures proper drainage and helps maintain fluid flow, reducing the risk of clogs. This design helps keep the waste moving toward the main drainage system, thus improving the overall functionality and efficiency of the plumbing setup.

While there are advantages to cost, flow, and installation ease, the critical aspect lies in the design principles that enhance drainage performance. The pitched inlets help counteract any potential buildup of waste or debris, which can be particularly problematic in urinal applications where waste can vary. This focus on effective drainage is why the pitch of the fittings is a significant factor in their preference over straight threaded fittings.