stop water from condensing on gas pipe?

Check at the hardware store for foam wrap. Goes around the pipe, and insulates it. Home Depot has it, both in rigid style, and also a bit softer style.
Also worth doing something about the cellar humidity. Dehumdifier, maybe? Or some ventilation to the outdoors.

Christopher A. Young
Do good work.
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
Add image file
Upload is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.