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This brown spot recently appeared on our master bathroom ceiling.

  1. This is a second floor ceiling. The attic is above this room.
  2. The HVAC is in the attic above this room. It's not directly over it, but it's close enough. We did have some unusually warm days last week where we ran the AC.
  3. The roof is around 8 years old, so it's reasonably new.
  4. There are no gutters on the side of the house where the stain is, so I don't think it can be a backed up gutter.
  5. We recently had the insulation in our attic topped up to R-60. I'm not sure it it's relevant, but it is new.

Any tips on who to call first?

I'm leaning towards calling out the HVAC folks to make sure the condensation line is draining properly.

Brown spot on master bathroom ceiling

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    With the HVAC being above the room, checking the HVAC sounds a good way to lean. If you can get into the attic yourself safely, you might also be able to see if new leaks have developed in the roof. Commented Nov 13, 2023 at 15:35
  • Keep an eye out for any evidence of new upstairs residents, as well. Squirrels have a terrible habit of moving into attics in the fall if they can find or make an opening.
    – Ecnerwal
    Commented Nov 13, 2023 at 15:46
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    You have a water leak. Could be the HVAC, could be a roof leak.
    – Huesmann
    Commented Nov 13, 2023 at 18:38
  • I would check the HVAC right away. A friend developed a small pool in his basement recently as not just the humidifier drain pan but also the condensate drain line were clogged with pet hair and dust.
    – eszed
    Commented Dec 14, 2023 at 1:48

2 Answers 2

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Being a DIY site, I hate to first off recommend calling in the pros but the AC guys would be my first choice. If your attic is readily accessible, go up there with a really bright flashlight and check out the AC unit. Check where the pipe/tube goes into the unit/pan to see if the water's draining out. You can pour in some extra water to verify it's draining and not clogged. Also check the pipe for any cracks where it could be leaking. Check the insulation around where the ceiling spot is to see if it's wet to try to determine where the water came from. Check out the roof for any water marks. Run the AC for awhile and check the pipes for any signs of condensation and also verify the condensate is draining outside.

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Thanks for the help with this. It turned out to be related to the air conditioner but, not quite how I expected. Here's what I did:

  1. I called out the AC company, and they initially said that there was a leak in the roof where the plumbing vent was. The attic insulation was wet below the plumbing vent pipe.
  2. Next I called out the roofer, and he confirmed that no water was getting in at the roof. The water was coming from the plumbing vent where the AC condensate line was draining.
  3. I called the AC company back out, and they rerouted the AC drain line away from the plumbing vent out through the dedicated pipe where it used to go before I had the new AC installed. This didn't fix the leak. 🤦🏾‍♂️
  4. At this point, I realized that where the AC installers had inserted the condensate drain line into the plumbing vent stack was not properly sealed, so whenever the attic temp dropped below the dew point, steam from the dishwasher or shower, or washing machine would rise up into the plumbing vent, condense, then leak out of the plumbing vent through the bad seal. I called the AC company back out and they replaced the bad t-joint and re-sealed everything. They are coming back out to paint our stained ceilings.

In other words, this was a big hassle that I am glad is resolved. Thanks again for your advice. 👍🏾

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  • I did not see this coming. Glad you figured it out!
    – eszed
    Commented Dec 18, 2023 at 23:18

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