I noticed some water dripping from my A/C's secondary condensate drain. The primary condensate drain line still has what seems like a normal flow of water coming from it, so I don't think it is clogged (may be partially clogged?). I went up in the attic and, sure enough, the overflow pan had a small amount of water in it. This water is coming from a fitting in the evaporator coil that looks like a PVC cap, but with a small hole in it: And an overview image: Notice in the bottom picture that the the primary drain has a float valve; I inspected this and it appears to be in working order, and it has not tripped (A/C running and cooling normally).
The question I have is what is the purpose of the fitting with the hole in it, and why might water be dripping from it?