What is the minimum drain size to serve a single sink?

The minimum drain size to serve a single sink is 1.5 inches. This size is established to ensure that the drainage system can effectively handle the wastewater produced by the sink, minimizing the risk of clogs and allowing for proper drainage. A drain size of 1.5 inches provides ample flow capacity for typical kitchen or bathroom sinks, accommodating the volume of water used in daily activities like washing dishes or handwashing.

Choosing a drain size larger than necessary, such as 2 inches or 3 inches, would not be practical for a single sink installation, as it could lead to increased costs and installation complexity without providing any real benefit in terms of drainage performance. On the other hand, a drain size smaller than 1.5 inches, such as 1 inch, may not adequately handle the flow, increasing the risk of backups or slow drainage. Therefore, 1.5 inches is the standard size that balances efficiency, cost-effectiveness, and functionality for a single-sink application.