AC Condensation Drain Advice

[Electrican]

These guys are on the right track! Educate yourself on positive vs negative, and go from there.

I have a negative pressure system, and the clowns installed it like a positive pressure. It took me awhile to figure it out why it was overflowing the internal pan and leaking thru the sheet metal into the galvanized overflow. If you have a negative pressure system, then both the primary & secondary drains need to have a p-trap in order to drain correctly. If left open to atmosphere, it will create a vacuum and not let the condensate drain.

Also, I like to have my inspection port on the upstream side of the trap so that my bleach has to go thru the trap too.

Thanks. I’m pretty well educated in the positive vs negative in the electricity world but not HVAC . I have had the unit serviced a couple different times and the “professionals” didn’t mention anything about it being wrong. It just puzzling that the water didn’t drain back into overflow pan and outside thru the viewing pipe

[JhuntsAlot]

I used to install AC systems when I was younger. To be honest, was always told the p-trap and vent for the sink was was good enough. Any access near the coil was for clean out and was capped. But that was also 20+ years ago.

Did find this website with some interesting info on this.

https://cfacservice.com/home-ac-repairs/drain-lines/

Good info on the drain setup. Specifically where the vent should be.

I do think the p-trap you have is not ideal. You should probably get an actual sloping trap and not have the 90’s.



J

[Hunterdan]

I just had a new A/C system installed and they told me to buy Main Line Cleaner from The Home Depot to pour down that drain pipe once a year to keep it clean.

[Starvin]

Thanks. I’m pretty well educated in the positive vs negative in the electricity world but not HVAC . I have had the unit serviced a couple different times and the “professionals” didn’t mention anything about it being wrong. It just puzzling that the water didn’t drain back into overflow pan and outside thru the viewing pipe

The problem has been addressed several times above for a simple fix. What you done should fix it, Suggest you test it. Then call a tech out to install a safety float switch and the tech can explain what happened when the tee outlet is lower than the main drain outlet (when the water backs up it will come out of the lowest opening) Good Luck

[jdavidson]

If it’s a gas system and the coil is IN FRONT of the blower ( trust me it is )... then get rid of the P trap.

P trap are necessary ONLY on negative pressure systems (electric)