[Yodrr]

I have 90 year old home with cast iron waste pipes. One 2nd floor bath sink gurgles, after cutting into wall behind sink I have cofirmed the obvious... sink isn't vented. The cast iron waste pipe rises 6" above the sink drain with a hub. This hub is filled with a very hard chocky white stuff. Doesn't seem to be sandy, so could this be concrete or some other 1920's pipe filler? Is drilling with concrete bit the only solution?

[ballengerb1]

Don't know where you live so this may not be allowed by your local plumbing code. You could solve the issue by installing a Studor vent or AAV. Has this sink always gurgle every day since you moved in?

[hkstroud]

I agree with Bob that an AAV under the sink is the best approach. However, if it is you desire or intent to install a proper vent line, I wouldn't try drilling out what ever was used (probably plaster) to seal the old cast. There must be a tee where the sink drain meets the drain pipe. I would try removing that section of pipe at that joint and using PVC to vent. Is that section of pipe cast iron or galvanized iron pipe. If galvanized I would cut it below the sealing material and convert to PVC with a rubber coupling.

[speedball1]

A little note.
Codes mandate that if you use a AAV that it must be assessable for service or replacement. In other words you can't seal it up in a wall. Good luck. Tom