I'm installing a few mini-split AC units in my house, and I'm trying to determine the best place to run the condensate line. Right now it's either between running it outside with the line set and tray cable, or sending it down to the basement and running it into the slop sink. Running it outside along with the line set is the easiest solution, but I'm worried about insects, enticed by the water and damp environment, climbing inside the line and either making a nest or coming inside the house. Is this a valid concern? Is there anything I could do to prevent that? Anything I need to consider when placing the condensate line?

This is a gravity drain.


Draining into sinks is not ideal. You have the plumbing in an inconvenient location and it tends to accumulate mildew. Outside is probably better.

One approach to dealing with the insect thing is a bell outlet with screening. Simply increase the size of the pipe dramatically at the outlet and install insect screening however is convenient.

  • I would agree outside is better, bugs really don’t like condensate it is slightly acidic the only thing that likes that water is fungus/ mildew in the tube, until it hits earth then the dirt adjusts the ph to normal.
    – Ed Beal
    Jun 24 '19 at 15:26

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