What would cause water to leak from the vent in the plumbing system?
Water should not be leaking from your vent system. The only water that should be in your vent system should be the occasional storm water after a big storm. There should be no way for sewage or sewage water to get into your vents or system. If you have a backup you would know from water coming up from the lower floors that you have a leak. Replacing the vent should usually fix the problem, if it doesn’t correct the problem – You know who to call.
