I was told by an AC tech, that the sec. pan was rusting out and needed to be replaced. After he left, I went up to see how the pan looked. The rust wasn't too bad, so I cleaned it out and put rustoleum on it. That worked, but I am concerned with what is causing the water to go into the secondary pan since it is my understanding that it only takes emergency overflow. I checked the pan for several weeks during the summer and no water appeared. Now that it has gotten more humid (we live in AZ), about a cup of water appears about once a week. Can this all be from condensation? All the pipes seem to be draining fine. What else might be causing this water to collect in the S.P.?