My a/c unit in the attic has a main drain pipe and then what I think is an emergency overflow pipe. The emergency is just an inch long and would dump water into the pan underneath, whereas the main drain goes to my sewer. About 6 inches from the a/c unit, the main drain has a T in it, with the leg pointing up. Both the leg of the T and the emergency pipe have a pretty strong flow of cold air coming out of them when the A/C is running. On the one hand, this doesn't seem right, but on the other, if I capped them, then the emergency would be worthless and I'd probably blow the sewer trap dry on the main line. Any thoughts on if this is the right or wrong setup?

I don't understand your setup. You have an open "T" that the main drain drips into or what?

i don't think its abnormal to have air coming out of that main. It IS plumbed directly into the air handler beneath the coils....which air blows over.

Maybe ask someone else, but I think its OK. I cannot remember if I noticed mine doing the same.

Air your filters clean in the air handler and/or air return?

[This message has been edited by jed1154 (edited 6/21/2011 11:18a).]

Thanks. I sketched something in case it helps with my description:

IMG >

That doesn't make any sense. The emergency line is usually routed from the pan out to someplace where you would notice it leaking, like the roof overhang. If your main drain from the coil clogs up, then it starts to drain into the pan below, thus letting the emergency drain work and then the homeowner will know what's going on. A picture would sure help though.

The drain pan itself has a drain and pipe which leads out of my attic, which would presumably take the water from the emergency drain pipe out of the attic.

You can expect cold air to come out of the T. It is tied into the A/C unit and takes the condesate from the cooling coils to the drain. So the drain it open to the samy system h air is cooled in..

I cannot see you sketch, but assume you ahve adrain from the metal "box" that runs out to a T. The t is open at the top and then water drains out the bottom to the sewer. The open end of the T allows you to pout chlorox in the line to keep algae from building up and clogging yur drin line.

The air should be small.

i've got the same thing. We have the "T" that points up from teh main condesnation line going outside the house, then a secondary/emergency drain that feeds into the pan and there is another pump for the pan that alarms if it operates. air does blow out from that T as you described and as indicated in your sketch. nothing to worry about. Just make sure the rest of your ducts are sealed, kept away from the roof deck, and not pinched off by straps.

[This message has been edited by DwightSchrute (edited 6/21/2011 5:02p).]

It is supposed to be that way. The T can sometimes be used as a cleanout for the P-trap that is a few inches past it. You should also use that T to pour a cup of bleach in it once a quarter. This helps to keep the line going to the sewer clean. If cold air is blowing out of it then it is a good indicator that everything is running properly.

What's wrong with simply putting a cap on the vertical piece of PVC where you pour the bleach in - and remove it when you need to pour in the bleach? It should still vent properly and drain into the sewer, right?

This can cause a vacuum and cause the system to back up to emergency drain. If you want to cover it I would use a cap loosely sat on it or a one way vent or a big ball of cotton loosely placed in the access pipe. Something like that.

IMG >

Here is a diagram I use on my reports. You have a primary and secondary drain. The primary should has the maintenance stub (you should pour some bleach down the stub a couple times a summer.) If the primary does not have the trap installed before the stub you will lose air through the hole. If it has no trap at all and the run to the sink (the most common termination point in newer construction) is short enough, many people notice a hissing sound and air coming through the drain of that vanity. The TREC also says that the trap should have pipe insulation on it.

The secondary line sometimes just goes to the drain of the pain then outside at the soffit. Some times they will have the secondary drain from the evaporator drain into the pan. Sometimes they will plumb it directly to the line going out and have the pan drain tie in with a "T."

If you don't have a trap, you can buy a trap fitting and install one cheaply. You can also buy a pvc cap and place it over the maintenance stub (don't glue it) so that it stops the air.