I noticed today that the side plumbing vent (just in the foundation) had some accumulated water and toilet paper around it. Not a lot, but enough to know that it wasn't there yesterday. Upon close inspection of the vent, I noticed along with the toilet paper, there is a bit of human waste visible. Again, not a lot, but enough to know that it shouldn't be there.

There haven't been any odors, no gurgling toilets. I did notice that the shower was draining a little slowly last week, but that problem has since disappeared. I had someone flush the toilet while I was in front of the vent and no water came out. Is this just a case of having an intermittent clog that has since gone away or am I looking at something a bit more serious?

Hi page and welcome, the "vent" your looking in could that be called a cleanout? Sounds to me like you may have a partial blockage or poor pitch on your drain. Can you see if the line might have a broken hangar? Or a sag in the line? There'll be a pro along shortly for a better answer, hang tight and good luck

Also it would be helpful to know if your on city or septic.

Hi page and welcome, the "vent" your looking in could that be called a cleanout? sounds to me like you may have a partial blockage or poor pitch on your drain. Can you see if the line might have a broken hangar? or a sag in the line? There'll be a pro along shortly for a better answer, hang tight and good luck

also it would be helpful to know if your on city or septic.

I'm on a city line. I've owned the house for over 5 years (it was built in the mid 1950's). I'm on a slab, so no basement. There have been several updates to the plumbing since then, so I'm not overly concerned with a huge, tear out my front lawn type of problem. It was just a little shocking to see.

I'm curious as to why you wanted to look in a cleanout without an obvious problem

There is no "side vent", only a roof vent or AAV. If you see directly into the cleanout, the cap is missing. What exactly are you considering a "side vent"?