siphonage: Why Houses Need Plumbing Vents (forget the soda bottle analogy) - 01/29/13 06:36 PM
When it comes to first time home buyers, one of the least understood components of a home seems to be plumbing vents.  You know, those pipes sticking up out of the roof that run through the attic and through the rest of the house.  All plumbing fixtures, with the possible exception of floor drains, require a plumbing vent.  Vents are frequently connected together inside the attic, which allows for less penetrations in the roof.

Plumbing vents prevent traps from being siphoned. Let me repeat that - plumbing vents prevent traps from being siphoned.  They also prevent back-pressure on traps, but … (29 comments)