siphon: 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)

siphon: A Primer on "S" Traps - 06/04/12 07:53 PM
A common plumbing defect found in many older houses is an "S" trap.  An "S" trap is named so because it looks like an "S" on its side - it basically consists of a normal trap, and then another trap installed right up against it in an upside-down fashion, as shown below.  These traps are prohibited by the Minnesota State Plumbing Code, but that doesn't mean you can't buy them at any home improvement store.

The most common places you'll find  "S" traps are at plumbing fixtures that aren't vented, such as an illegal basement bathroom sink, a DIY basement bar … (20 comments)