Hi, I have a drain blockage in my kitchen I have not yet been able to clear. I went on the roof to try to snake down the vent. The vent seems to be blocked about 2 1/2 feet down. With a flash light I see no nests or debris.... It is as though it is intentionally blocked like it is an abandoned vent although it is in the right spot for the kitchen ( sorry for the confusion as we did major remodel 5 years ago which required adding vents).... Is there a reason the vent would be blocked and should I just break through it?