Water in vent pipe

[Jumpmanil]

As I was up in the attic yesterday installing new lights, I noticed a PVC pipe that was detached but wasn't sure what it was. I saw/heard/felt that there was water in the pipe and that some was leaking out the open end. After draining a couple of gallons out, I traced it to see that it is the vent pipe. It seems that it has been disconnected for some time, since the ends don't even meet up. The one end is going to a bathroom and washing machine, the other end to the rest of the house.

Question #1 - Should there be water in the pipe at all?

Question #2 - Do I try to reconnect the ends or could it have been disconnected (or not connected to start with) on purpose?

Thanks,
Bryan

[master plumber mark]

water in the vent pipie hapens because of rain
and condensation... and it is best to figure out
which end is th one going up to the roof and make sure
you give it fall the other way downwards