Is this correct?

We recently had a tankless hot water heater installed. There was an existing metal vent tube that the plumber then Installed the pvc pipe inside of. Initially I was worried about rain leaking, as they only had some sort of flat plastic flange outside; and sure enough it did leak down into the garage when it rained. They then came back and added a rubber seal outside. Can anyone clarify if this is correct?

We recently had a tankless hot water heater installed. There was an existing metal vent tube that the plumber then Installed the pvc pipe inside of. Initially I was worried about rain leaking, as they only had some sort of flat plastic flange outside; and sure enough it did leak down into the garage when it rained. They then came back and added a rubber seal outside. Can anyone clarify if this is correct?