Round Thing on Roof?

What are these round objects protruding from the roof of almost every house?

Through the years as plumbing became prevalent in most homes, there arose this great odor. It turns out that waste water will become stagnant, among other things and foul up the air in your house.

In comes the invention of the p-trap. The p-trap allows a small amount of water to be held in a valley in the plumbing. This prevents the malodorous gases from returning back in to the house.

But, what does that have to do with the roof and this round thing? It is a vent. Without venting the small amount of trapped water is vacuumed or siphoned out of the p-trap allowing the odors to return.

Truth is these vents rarely cause problems in the plumbing system. The greatest problem here is roof leaks.

Over a period of time the rubber boot can deteriorate and crack letting water in. Improper installation is also a potential hazard. This is just one of the many things checked during a home inspection. Vent or funnel, we find out. #ffhomeinspect