Icy Stink Pipe

I've noticed that there appears to be excessively moist air coming from my stink pipe, which freezes in the winter. i see ice clinging from the mouth of the pipe, as well as at a spliced (pvc) joint. it will melt in the sun, and drip off the roof into my garden, and generally cause the area to smell- i note a lot of gaseous odor as well in the colder months. I've recenty had my septic tank pumped, to no avail. Is icing like this normal?

thanks for any suggestions!

hi & low

Weather systems can have an effect on plumbing venting.Hi will push gases
back into sewer.Lo will let it rise and because moister in gasses will freeze
creates that ring.Do not worry.

yeah, i haven't noticed any negative side effects other than massive icing- never seen the phenomenon anywhere else.