Air Conditioning - First time poster needs help with a leak.

ok. my central air system is leaking from where the drain tube attaches to the furnace. there is a two outlet valve. one has a red plastic plug and the other side goes down pipes to the drain. water is dripping out of the red plug. this is my guess. the drain line is plugged and water is coming into the plug. i think the plug is designed to leak a little to tell you the drain is plugged. if i unscrew the plug there is a hole the size of a pencil eraser at the top of the opening. the drain side fittings are glued together so i don't want to break them to check. what should i do? thanks for the help!

One of the easiest ways to clear a clogged drain is to hook a wet/dry vac to the outlet of the drain & suck out the clog. After clearing the clog & allowing the water to drain, shut off the A/C, remove the red plug & using a turkey baster or something similar, add some bleach to the drain pan. A third to a half cup of bleach is plenty & allow this to drain out of the now cleared drain line. Re-install the red plug & turn your A/C back on.