Improper installation

When inspecting air handlers I am finding more and more unused condensation drain outlets are not plugged. I report it as a concern. Is this a legitimate concern and if so, why.

I have never seen them completely unplugged but I have seen the plugs half in/half out. Even with them half in, there is a considerable amount of conditioned air being blown through it. I push them back in and move on but I would say it was a concern because of that reason. Same goes for trapless lines that have conditioned air blown out of the pvc vent for the line. What do you guys say to this?

I feel they should caped after installation because they let unfiltered air into the system as well as insects and rodents. The installers are just lazy.

There are two types of drains. Positive pressure, where evaporator coil is on discharge side of the blower; and negative pressure where the coil is located on the inlet side of the blower. Negative pressure drains must be trapped to allow proper draining of the water. In addition a vented tee assembly must be installed at the outlet of the trap. This prevents air trapping of the water in the drain line by breaking the negative pressure after the trap. Capping such a tee could result in back up of water. A better solution if it is deemed necessary would be to screen the opening to prevent insect entry.