Upstairs bath sink not draining. No apparent clog either at p-trap or down line. Turned off AC to test and noticed sink starts to slowly drain. Am I getting air in the line from the AC unit via the condensate line?

Why do you think no clog?

Maybe try to clear it out with really hot water and dish soap?

JobSecurity said:

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Clog is probably just further down the wall than you think.

I hate whoever came up with this design. If the pipe clogs the sink overflow doesn't work which means the AC fills the sink and floods your bathroom. There has to be a better way

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I had clog 10+ feet down the line in the wall after AC guy blew out condensate line.

you try the shop vac method yet?

JobSecurity said:

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Clog is probably just further down the wall than you think.

I hate whoever came up with this design. If the pipe clogs the sink overflow doesn't work which means the AC fills the sink and floods your bathroom. There has to be a better way

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For real. If the person who came up with this was in front of me I'd beat them with a rubber hose. We have dealt with this every summer, on a second-story bathroom that would do thousands in water damage if we didn't catch it in time (luckily we always have).

I had this exact issue a few months ago. Cleaned the traps, tried to blow out the line, snaked it myself with a little handheld snake and didn't seem to run into anything. I even tried drain cleaner and hot water. Ran out of time and called a plumber, and he found a clog further down with his much longer snake.

I'd bet money it's clogged somewhere.

JobSecurity said:

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Clog is probably just further down the wall than you think.

I hate whoever came up with this design. If the pipe clogs the sink overflow doesn't work which means the AC fills the sink and floods your bathroom. There has to be a better way

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This just happened to my MIL. The condensate drain line is tied into a sink in her guest bathroom that only gets used when company comes into town. The two adjacent bedrooms got flooded before she found it. Thousands of dollars in damage.

Once the weather cools down I'll be up in her attic re-routing the line to the vent pipe. I realize this is wet venting and technically against code, but at least I know that the sink won't clog again, and the sink drain is never going to pull enough suction to suck the water out of the AC condensate line trap.

https://www.homedepot.com/p/Milwaukee-M12-12-Volt-Lithium-Ion-Cordless-Drain-Cleaning-Airsnake-Air-Gun-Kit-with-1-2-0Ah-Battery-Toilet-Attachments-2572B-21/303169749


I had the same problem earlier this year. I took off the p-trap and blew into the PVC drain in the back of the wall under my sink....heard a THUMP....problem fixed. This Air Snake has paid for itself in my house 10x in the last few years!

rme said:

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JobSecurity said:

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Clog is probably just further down the wall than you think.

I hate whoever came up with this design. If the pipe clogs the sink overflow doesn't work which means the AC fills the sink and floods your bathroom. There has to be a better way

---

I had clog 10+ feet down the line in the wall after AC guy blew out condensate line

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Same, I ran a 25 ft snake down my upstairs bath sink to clear it out

A decade ago when we bought our 1977 home in Klein I ran into a sink draining slowly and then caught it backfilling as mentioned before. Traced it up into the attic and found the condensate line plumbed into it. It had a cleanout with a capped top. I had to snake 40 yrs of neglect out but afterwards it was right as rain.

Every year, around new years, I drop a couple ounces of liquid pool shock/sodium hypochlorite down the clean out, wait 10 minutes, and then drop a milk jug of water down the clean out as a rinse above that sink, and run the sink for a minute.

Never had any issues since then BUT that sink is in a guest bathroom. If it had folks combing hair or shaving their faces I imagine it would need more love. YMMV.