What is the standard diameter for residential drain pipes used for most fixtures?

The standard diameter for residential drain pipes used for most fixtures is typically 2 inches. This size is appropriate for a variety of fixtures including sinks, bathtubs, and other drainage systems in residential settings. A 2-inch diameter pipe provides an adequate flow rate to accommodate the wastewater produced by these fixtures while also ensuring that they are effectively vented to prevent issues like siphoning or negative pressure.

Using a 2-inch pipe strikes a balance between efficient drainage and the ability to manage larger volumes of wastewater without the risk of clogging. This size is commonly recognized and accepted in plumbing codes, which provide guidelines for plumbing system design to ensure functionality and safety. Knowing this standard is important for inspectors to assess whether the plumbing system in a home meets code and performs properly.