jimkp

Is it standard for the HVAC guy to tap the vent pipe and combustion-air pipe together prior to exiting the foundation wall? I recently had to look at some work an HVAC guy installed, and there is a tremendous amount of condensation forming (and leaking) from the vent pipe coupling.

Bestheating

Tell me if I am wrong, but what you might have is called a concentric vent termination. Inside, it will have one pipe going in straight and another going in at a 45 degree angle. On the outside it will be a cone shaped affair. If there are two seperate pipes coming out, stop reading.
Ok, if it is a concentric vent, try the following: Your condensation should be from the pipe which is going in straight (the exhaust). Follow this back to the draft inducing motor to confirm it. You might get lucky and the installer forgot to glue it together as your source of condensation. If so, try pulling off the cone on the outside. The pipe in the middle just might pull straight out and you can finish the job. Let me know how you do!
Larry