I need some help on a sink that won’t drain and I can not figure it out. The sink is in our upstairs bathroom. The AC line drains into it from the 3/4” line into the brass fitting area. When I take the P trap off, there is a slow trickle from the AC. The P trap under neath is 100% clear. On the main drain line, I can only get my snake about 18”-20” deep before a hard stop. If you run the sink for about 8-10 seconds, it fills back up and won’t drain. Any ideas?

Run snake down nearby roof vent ?

Only way is to scope it/snake it from the vent pipe On the roof first then down that Main drain.

If you can’t get the snake down the drain you’ll have to rent a scope and see what the blockage might be.

Calling a plumber will run you about $300 for service call and snaking both pipes.

Skip the drano solutions - doesn’t apply here and it’s never worked for me.

My eye just started twitching after seeing that pic. I sure hope you don’t have 2 sinks right there

Your ac drain is clogged. I had the same thing happen to me. The suction of your ac line being clogged causes the backup. I don't understand the physics of it, but when I cleared the ac drain, the whole thing started working properly. I now pour a cup of bleach down the ac line 2x a year to make sure it stays clear.

Yup, my washer clogs that one once a month and it pisses me off.

Call The Drain Doctor. Will be under $200.

Alert Drain also very good, (972) 285-1541

Wait until about 3pm before getting on your roof to snake it. It will unclog easier.

I have a 25' (I think) drain snake if you need to borrow one.

Try to blow it out with a compressor through your A/C line in the attic.

This.

this will fix it for sure...

https://www.amazon.com/Thrift-T-200...&hvtargid=pla-569507915723&psc=1

Ac repair guy told me last week not to use bleach only use vinegar

Texas Dan starts a new thread about it each year.

I had trouble clearing a stoppage like this that was due to the AC drain. What finally worked (done it twice) was to disconnect the AC line (if you can) and use a shop vac to get the line clear. It wasn’t a fun job.

Yep, shopvac the PVC pipe outside, and if that doesn't work then snake the line from up top at the same time. Nasty

The newer ones somehow worried out the prob.em.

Looks like a problematic design. A slow drip of AC condensation making two 90° turns is an opportunity for water to be static. Something similar caused this white, pasty crap to build up in my drain once. I opened it up near the unit, got some really hot water in the line and freed it up. I'd look at a way to put in one 45°, or flexible hose where you have those 90°'s.

Is your unit setting on a drip pan?

I don't see how a clog in the a/c drain is going to affect the draining of the sink, the vent for the sink drain is down stream of the a/c tie in. The fact that the a/c still drips when the p-trap is off says the a/c line isn't blocked.

My a/c drain line gets blocked up all the time I hate that damn thing I could shoot the person who put it in the attic, I will never own a home again with the air handler in the attic!

My kids would clog their drains every other year or so because they would not run much water after spitting out their toothpaste. It would gather about a foot or two into the pipe and pretty much turn into mortar. After cleaning it out a few times and talking to them about running more water I had them take it all apart and clean it out themselves. Never happened again after they had to fix it.

If your drain is straight out then try a piece of rod to break up the clog. If there is a turn then you might try and electricians fish tape, they are pretty sturdy. Put it in there up to the stop and then start twisting it in circles. Take it out and see if there is anything stuck on the end. If so then keep at it, you are making progress.

The 3/4 from the condensate is not clogged. The sink drain is.

Looks like a good device, have you used it?

I have, they work great as long as it blasts the blockage out. If it doesn’t you’ve got to let it bleed off and makes a mess.