We had another condensation leak at our upstairs unit last night. It happened for the first time almost exactly a year ago. House was built in 1990 and the unit was replaced in 2017. I've been dumping vinegar down the drain religiously since we had the first leak last year.

What else should I be doing to keep this from happening again ? Fortunately this time we caught it early and didn't have any residual damage. The AC tech that's here said adding a J trap might help but I don't understand the logic behind it.

where does it tie into?

If it's a sink drain, you might want to snake it and make sure there isn't a hairball partially blocking it up or something

Every Ideas of humid July my buddy's attic AC would leak through the ceiling and when finally replaced, mold was found in this old-timey flattish drain pan.
The newer pan was more akin to a funnel but it was made to leak with foam insulation disforming it.
The replacement to this also leaked BUT this was poor/old plumbing that a plumber fixed and now finally NO leaks for over 2 years.

Lessons learned:
SlimeOut tablets into pan during AC season
Biannual checks clean, level pan & blow out pipes
New plumber visit should include new piping for HVAC - a simple job but don't allow service door blockage
New HVAC shopping should include a preview of pan

The primary drains to the outside of the home.

I'd blow the line out with some compressed air

sts7049 said:

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I'd blow the line out with some compressed air

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+1

I got lazy this year and ended up with a clogged line.. the snake wasn't cutting it so I broke out the air compressor.

I can't tell if you have a float switch in the top left of the photo but if you do it looks higher than the top of the T fitting. If you do have one it's probably overflowing before it trips the switch so I'd add a piece of pipe to the top of the open T.

If you don't have a float switch then get one installed and you'll figure it out when the AC stops cooling..

Yea the secondary has a float switch (I think) but the primary does not so we definitely need to add that.

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

get one of these. worth it's weight in gold!

ReloadAg said:

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We had another condensation leak at our upstairs unit last night. It happened for the first time almost exactly a year ago. House was built in 1990 and the unit was replaced in 2017. I've been dumping vinegar down the drain religiously since we had the first leak last year.

What else should I be doing to keep this from happening again ? Fortunately this time we caught it early and didn't have any residual damage. The AC tech that's here said adding a J trap might help but I don't understand the logic behind it.

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There should be a Tee where it first comes out of the coil. That is where you add 1 ounce of bleach at to keep it clean. I do this on all the units i maintain in early March every year and rarely have any clog issues. I would cut it all out and use new 3/4 and add the tee at the beginning right next to the coil.

ReloadAg said:

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The primary drains to the outside of the home.

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No need to have a trap if it is not tied into a drain line that terminates to sewer or septic