This is a topic that impacts all of us including realtors, home inspectors and home buyers. In new construction it seems to almost always be done correctly, at least in my area. But in older homes and mobile homes, plumbing vent stacks can be really messed up or missing completely. Venting the drain and sewer system seems like a straight forward enough concept. The vent pipes go up and outside, through the roof usually. If they terminate under eaves, are cut off in the attic, terminate in front of a window that opens, that is yet another installation problem. My topic here will discuss homes with too few or no vents at all. The roof you see below, was a home that had NO sewer vents at all. There was no main, nothing in the kitchen, bath, etc. As a result, drains were gurgling and slow. Often in older homes, especially mobile and manufactured homes, they try to help the situation of missing or too few vents by putting in mechanical vents. These devices can help alleviate a slow drain, but they are sure not as good as a real vent. They must be installed at the correct height above the flood level of the basin. Also, as they are mechanical, they will fail at some point and, at that point, they will allow sewer gas out into the home. If you think about it, the need for vents, and how they work, is pretty basic and intuitive. Think of the big juice can. You make a large hole in one edge and when you pour it goes glug, glug, glug. Yet, put the teeny, tiniest hole at the other edge, and it comes out smooth like gangbusters. A home inspector should always take a look at the venting. A stack missing at a small sink is one thing, but when the main stack is no where to be seen that indicates pretty hay wire plumbing.
No vents at all, anywhere in home Mechanical vent
Give it the juice test!
Thanks for dropping by,
Steven L. Smith
Bellingham WA property inspections