What is the minimum internal diameter for a condensate waste drain line?

The correct minimum internal diameter for a condensate waste drain line is ¾ inch. This specification is grounded in the need to ensure adequate drainage of condensate from HVAC systems without risk of clogging or insufficient flow. A drain line with a diameter of ¾ inch strikes a balance between being large enough to handle the volume of condensate generated by typical systems while remaining manageable for installation and maintenance.

Choosing a diameter smaller than ¾ inch, such as ½ inch, may not effectively accommodate the flow requirements, potentially leading to blockage and overflow issues. Similarly, while 1 inch and 1½ inch are suitable for larger applications, they exceed the minimum requirements for standard condensate drainage, which can lead to unnecessary material use and complexity in installation. Thus, the ¾ inch diameter is designed to meet the most common needs in a practical and efficient manner.