What should be the minimum size of a drain for a bathroom sink under normal circumstances?

The minimum size of a drain for a bathroom sink under normal circumstances is established in plumbing codes to ensure adequate drainage and prevent clogging. A 1.5-inch drain size is recommended because it allows for sufficient flow of water from the sink while also accommodating any debris that may be washed down with it, such as soap residue, hair, and toothpaste.

Choosing a 1.5-inch drain effectively balances the need for a larger diameter to reduce the risk of blockages while still fitting within the constraints of typical bathroom plumbing fixtures. This size is also standardized in many plumbing codes, including the Massachusetts Plumbing Code, which mandates that this dimension will meet the needs of most residential bathroom sink installations without compromising performance.

Smaller drain sizes, such as 1 inch or 1.25 inches, may lead to slower drainage and increased clogging risks, making 1.5 inches the most appropriate choice for maintaining efficiency and reliability in a bathroom sink system. A 2-inch drain, while capable of handling higher volumes of water, may be considered excessive for a standard bathroom sink application, leading to unnecessary material costs and installation complexities.