ac condensate leak ceiling
https://getaustinroofingcompanyleaklab.quillnesty.com/posts/how-to-spot-a-roof-leak-vs.-ac-condensate-austin-roofing-company-leak-guide
I noticed a water stain spreading across my living room ceiling, right below where the AC unit sits in the attic. After poking around up there, I found the condensate drain line had come loose, causing a slow leak that was soaking into the insulation and drywall. I had to patch the pipe and replace the damaged ceiling board, plus repaint the whole area to cover the yellowed watermark.