What is the best way to clean out the plumbing roof vent? My toilet flushes too slowly and there is no obstuction in the toited itself causing it. I think it is the roof vent that may be clogged. What is the most advisable and effective method to clean it out? Is putting water from a garden hose down the vent any good or effective or do I need to roto root it out? Any suggestiions?