So I've been noticing a lot of water puddling under our upstairs bathroom sink lately.

I know it's got the AC primary drain line flowing into it. I took about the J-bend and checked to make sure it wasn't clogged. Cleaned it all out, put back together and then poured a cup of bleach down the PVC pipe in the attic.

This will be our 3 summer in this house and first I've seen this get that wet and that much condensation.

Photo with smaller puddle is after I took it apart and cleaned it all. Photos with larger puddle is after I cleaned it all up the first time to try and diagnose.

Am I missing something about what this could be? Trying to avoid a plumber but maybe that is the route we need to go.

is there a ptrap between the attic unit and the sink? Should be...this will keep a barrier that will prevent cold air from being pushed through the pipe into your sink line.

Also since the water is cold, coming into your house...if you have a high humidity house then this is hot helping. You could wrap the pipes under the sink I have seen as as suggestion.

I agree, insulate the condensate line and P trap.

Thank you fellas!

Upstairs sounds like it could see light duty. I would insulate the lines, put a catch tray on the cabinet bottom and if a guest bath- leave the cabinet door open/cracked.

CapCity12thMan said:

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is there a ptrap between the attic unit and the sink? Should be...this will keep a barrier that will prevent cold air from being pushed through the pipe into your sink line.

Also since the water is cold, coming into your house...if you have a high humidity house then this is hot helping. You could wrap the pipes under the sink I have seen as as suggestion.

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Update: I left the cabinet door open, condensation gone but did see a smaller puddle of water. Will get catch bin for it.

Also did some digging through the insulation. No ptrap. Only a 90 degree bend as it comes out the attic unit, water is running flowing through the pipe down. Pipe just goes another 4-5ft before taking a turn to go down to the bathroom sink.

Can also hear air sounds coming from sink bowl drain - is that a sign?

Bathroom is our only bathroom upstairs so gets used regularly for bath time and brushing teeth/hand washing.

Will still work on insulation of the piping under the kitchen sink, but I just am curious why it's now all of a sudden having this vs the past two summers of nada

This spring/summer seems like it is painfully more humid than usual. Probably from El Niño.

Huh...I had no idea a p-trap was needed...I'm pretty sure I don't have one on either AC unit and now I'm wondering if this is why I sometimes hear gurgling and/or airflow from our master bathroom. I had assumed it meant I had gunk built up in the line such that it was time to go pour bleach or vinegar (NOT AT THE SAME TIME) down the line.

I feel like every house I've looked at (including mine) has had the AC condensate drain somewhat haphazardly tied into bathroom plumbing such that it is begging to get clogged or start leaking. Are there not plumbing codes for such a thing?

I found this article interesting regarding where the p-trap should be in relation to the vent-t (spoiler: p-trap should be before the vent-t). I always thought the vent-t was simply an opportunity for random insulation/dust to get in and clog the line.

https://russellking.me/2012/09/22/no-its-not-a-pee-trap-so-please-dont/