I installed a 3" to 3" donught yesterday so I could transition from my cast iron hub to pvc wye. This morning I noticed a small amount of moisture sitting where the pcv and donut meet. It was a tight fit to get the pvc in the donut and tight going into the CI hub. Any ideas? Im not over concerned because it's such a small amount just curious if anyone has had this happen? I cant see how water would wick up between the rubber donut and pcv pipe (no pressure on the system either).