Our AC condensate line runs into our bathroom sink. AC was recently serviced and water was flowing fine. However, water is still dripping in the pan and going out the overflow drain in the backyard.

I opened up the drain line under the sink and after a few seconds a good amount of water flowed out. No blockage, but it's almost like it has a bubble in the line that's keeping it from flowing into the sink correctly. I've pulled the slip-joint and made sure it's clean.

Here's a pic of our setup, would be interested in y'all's thoughts on what may be causing this and potential solutions.

where is your unit in relation to the sink? If it is above the sink level (assume it is), then that slight curve upward on the hose under your sink probably isn't the issue, although it does mean that water is sitting in the line - much like a ptrap on your sink or toilet.

If when you took it off and water flowed that tells me the line isn't vented properly. Take a pic of what you have coming out of your unit and that might be a better indicator of what is going on.

I bought one of these: https://www.amazon.com/dp/B07THM2122?_encoding=UTF8&psc=1&ref_=cm_sw_r_cp_ud_dp_M1BPMMVX9MJ1YTK1AJQX

I had chronic line clogging problems but that was due to a) lines being old and b) the crazy route they took from the unit down to the sink. That little CO2 gun solved it and now I just use the bleach down the pipe more often and the issue has never come back.

Did you check the P trap on the sink ?
Also the sink drain could be clogged in the wall.

I have seen both happen when an ac drain is tied in. Also that black hose is normally done with a clear hose so you can see potential blockage. I would blow compressed air down that line in the attic to make sure it is not clogged from there to the sink trap. And once it is flowing pour a few ounces of bleach down that drain line.

If you fill sink bowl with water does is drain ok or is it slow ?


Post a pic of the drain line where it ties into the ac coil

Many times we find that nipple from the plumbing trap clogged with goo. If water poured out of the hose it would seem to me that the line up to the unit isn't clogged. Did you look into that little nipple to see if it was clear? A picture of your drain at the unit would be helpful. If you have a furnace the drain line is on the positive air side (blowing) and should have a vent stack in the drain that is not capped, if you have an air handler you have to have a P trap in the drain and it needs to not have any open vent between the unit and the trap but should have an open vent after the trap. Hot hot water is your friend if you have a vent that you can pour it in to try and flush the drain. One fear I have though is that you said "the AC was recently serviced". Many many times I have found that the technician accidentally broke the drain pan trying to get access into the drain or the coil to clear the drain causing water to drip into the overflow, it's even happened to us before. I'd start with the nipple on the sinks trap and work up from there. Keep us posted.

Yep, checked the ptrap on the sink, everything is cleaned out and looks good. Water is flowing fine. Again, no blockage from the ac to the sink. Added a pic.

Have run hot water down the condensate pipe even after the service just in case, but water flowing fine.

Have called the ac company to come back out since bi-annual service was last week.

Thanks again for your feedback! Will let you know what I find out tomorrow.

I think I've been on a dealer fishing trip or to Costa Rica with the owner of Murray air if that's the company you're using…. Small world.
It looks like the PVC coupling going into the air handler is newish. I'm starting to suspect the pan got cracked. Sometimes you can take a mirror and look at the bottom of the black female threaded part of the pan and see a hair line crack. It doesn't take much. I hope your AC company is honest and treats you right. I can't remember much about Mr Murray other than I think he sells a lot of American Standard equipment now. Keep us posted. Thanks for the picture.

Update:

Tech and supervisor deduced that our system may be sucking the condensate back into the unit, partly because of the shallow condensate line trap. Apparently most installations now have a deeper one, so we added that, he also added a valve for easier line clean out in the future. Not sure why after 15 years it's started doing this, but alas…

As of this morning no dripping from the overflow pipe outside but need to check again when I get home this evening to see if the pan is dry.

Final update:

Checked the pan and it's dry, so seems this fixed the issue. Here's a pic of the "deep trap".