Can anyone tell me why they would have extended this plumbing vent so tall? The toilet doesn’t flush real well, and this vent is directly above that toilet. It is the only plumbing vent on the house. I was just wondering what the point to extending it 4 feet would be?
http://www.nachi.org/forum/attachment.php?attachmentid=5048&stc=1&d=1155518045
Minimum heights are specified, but I know of no maximum. However, the height should not affect its function.
Are you sure that’s a plumbing vent?
Yes, its a plumbing vent. You can see where they added on the extra pipe. As far as I know, the minimum is 12 inches above the roof. I am just curious as to why they would extend it?
does this arae get a lot of snow that would be my thoughts
Roy Cooke
Roy,
No, Missouri can get a lot of snow on occasion, but none of the other houses around here have vents this tall. Most are fairly close to the 12 inch mark. Like Mr. Pope said, the height shouldn’t effect the operation, it is my own curiousity about why they would extend it. I just can’t think of a good reason for doing so. 
I’ve was told by another inspector that when con artists come through a neighborhood and find a mark and they’re doing HVAC work, one of the ways they leave signs for other con artists is by extending vents… like the one shown in the picture.
LOL! That is the most logical explaination for this that I have heard! Are you serious? This is not an inspection of mine…it is actually the house my girlfriend rented about a month ago. It has been bugging me ever since I first saw it. The owners of the house live right across the street…I will ask them if they had any work done. Thanks for the info!
That’s just what I was told. If it turns out the owners had work done, find out what they paid.
Ran across one like that a year ago. When I checked the code it was too high. If memory serves It’s not supposed to be more the 3 or 4 inches above the adjacent roof. Do not quote me on this Check it out first.
One possible issue. I’ve heard of extension to eliminate sewer gas smell from blanketing the yard, and extending the pipe higher would allow the prevailing winds to take it away, but there is also filters that can be fitted onto the pipe. Or a previous home inspector recommended the 10-foot/ 2-foot rule when the previous owner purchased the home!! HA! Who knows…
**SECTION 904
**
VENT TERMINALS
**904.1 Roof extension. **
All open vent pipes that extend through
a roof shall be terminated at least [NUMBER] inches (mm) above
the roof, except that where a roof is to be used for any purpose
other than weather protection, the vent extensions shall be run
at least 7 feet (2134 mm) above the roof.
Looks like ICC goofed when producing the latest CD version. As you can see no inches/mm listed. However I find the 7’ comment interesting. Is there a second story deck or bedroom window anywhere near the vent stack?
**904.5 Location of vent terminal. **An open vent terminal from
a drainage system shall not be located directly beneath any
door, openable window, or other air intake opening of the
building or of an adjacent building, and any such vent terminal
shall not be within 10 feet (3048 mm) horizontally of such an
opening unless it is at least 2 feet (610 mm) above the top of
such opening.
No worries Will. They’ve corrected in for '06. The minimum is 6".
There you go…that’s what I thought, too. 
Get the thing up into a good wind and you might get a venturi effect across the top of it and really reduce the effectivness of the vent to draw air.
Larry
Up high enough, it has the potential to freeze shut with enough moisture escaping.
Gypsies, actually… was the term he used. Said he’d done some research into it. I did a ride-along with him and we were in a tract. He pointed out a home with a vent about like the one in your photo. He said they typically add a whole section.