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YerDugliness 01-22-2010 04:54 PM

Can a roof vent identify where my main sewer line exits the house?
It looks like I will have to spend the weekend getting VERY well acquainted with a rental "roto-rooter'. My problem is that I cannot identify where my main sewer line exits my house and there is no clean-out outside. I intend to remove a (hopefully only one!) toilet to access the large sewage line with the roto-rooter, obviously I hope to remove only the toilet closest to the main line.

My house is oriented with the front door facing north. I have a full bath in the master bedroom at the southwest corner and a full bath located at the center of the east side of the house. My city's engineering department was no help, as the house was built in the late 1970's and all the engineering records from that long ago are in a warehouse somewhere. The only thing I got was a .pdf file showing that the water supply lines run along the street curb on the north side of the house and that the city's sewer lines run along the property lines on the south side of the house--nothing showing exactly where my main line connects to the city's sewer system, though, just the city's line.

I'm hoping that the house's sewer line's "vent" system will help identify where the main line exits the home. I figure it must be close to one of the toilets, each of which is within a foot of its respective east and west walls.

I can see a large (4"??) white PVC plastic vent pipe sticking up through the roof right above the exterior wall in the area of the bath at the southwestern corner. I can see various other smaller (2"??) vents sticking up through the roof near other locations, none of which are directly above the exterior wall as is that single large vent pipe---close to the kitchen, where the washer/dryer are in the garage, the restroom on the east side, but no other pieces of white 4" pipe anywhere. seems logical to me that the main line vent ought to be that large piece of PVC sticking out the roof and that ought to be where the main line exits the house, but I'm no plumber, so it also might be logical that the vent needs to be located at the far end of the house's main line and that it actually exits at the restroom location on the east side of the house. I could sure use some help from some of you knowledgable plumbers on the forum.

Thanks in advance for whatever help you can provide!

Dugly :cool:

MI-Roger 01-22-2010 05:13 PM

No basement or crawl space access?
Assuming the sewer line is located below the roof vent is not foolproof, but makes enough sense for this location to be your starting point.

It would be nice if the city could at least tell you how deep the line is. I'd hate for anyone to dig 4-feet in the right spot, abandon the location after not finding the line, then trench the entire yard loking for a pipe that is really 4'-6" deep.

Good luck.

YerDugliness 01-23-2010 07:21 PM


Originally Posted by MI-Roger (Post 387232)
Assuming the sewer line is located below the roof vent is not foolproof, but makes enough sense for this location to be your starting point.

Good luck.

Thanks for that info! I did some further searching on the forum and found that right below this thread there are some suggested topics that might relate to this issue. This one was particularly interesting b/c it shows a setup very much like what I believe mine to be, the only difference being that the wall in this video appears to be an inside wall whereas the wall where my 4" roof vent pipe appears is the outside wall for the house.

In this video it appears that the vent line is installed at the highest point in the course of the sewer line, everything runs downward from there and the sewer line eventually exits the house through the foundation. If the vent line is always installed at the highest point, I think the sewer line would have to exit the house on the east side, not at the SW corner.

I have another question.....or, actually, a couple:

Does each toilet need it's own 4" vent pipe? I can find only one 4" vent pipe in the house and it is very near the SW corner of the house.

Can I tell the "direction" of the main line flow by the direction of the curvature of the pipe beyond the toilet flange onto which the toilet mounts?? I could possibly take off one toilet, probably at the east side first, to ascertain which way the waste flows (again, hoping to find that the sewer's line exits my house on the east side).

So, any other ideas from anyone else? Thanks!

Dugly :cool:

wirenut1110 01-24-2010 08:35 AM

Is your house on a slab?

YerDugliness 01-24-2010 11:59 AM


Originally Posted by wirenut1110 (Post 387958)
Is your house on a slab?

Yes, it is slab construction.

Dugly :cool:

YerDugliness 01-24-2010 01:20 PM

Well, here's an update.....I managed to get one toilet off the flange and got about 50' of RR flex down the drain hole.......Murphy's Law must be in effect, it made a wrong turn and went up the 4" vent pipe, now I have 35' of flex sticking out of my vent.

At least we know the vent is not plugged.....will see if I can get it back down and start over.

Sadly, the other toilet, the one on the east side of the house, won't come up.....the hold-down hardware appears to be a plastic hex-shaped knob with the hex head of a "lag bolt" embedded in it. One of them came off, the other appears to be stripped inside the molded plastic knob. I'll change all that out when I get this done......IF I get this done!

Onward through the fog......:mad:

Dugly :cool:

Thurman 01-24-2010 01:33 PM

"Yes, it is slab construction" That's an "OUCH" to start with! One useful tool I have (and I understand everyone doesn't have one) is a piece of 3/8" round steel rod about 36" long with a 1/2" diameter piece for a handle. How is that a tool for this? IF I really cannot locate the main waste line coming from a house, I take this tool and start pushing it into the ground while twisting it. Even with the red clay soil in my area it will go in. Oddly enough, I've learned how to detect when I hit a rock or PVC/DWV waste lines. I've never seen cast iron used on slab homes but have experimented with this tool and found that locating cast iron piping will produce a "squeaking" sound when hit. It's not fool-proof for sure, but it does work a lot of times. Being as you know the city's sewer line is on the South side of the house, you should be able to locate this line with something like my tool and then find (hopefully) a "combination" clean-out just outside the wall of the home. Good Luck, David

YerDugliness 01-24-2010 03:44 PM


Originally Posted by Thurman (Post 388211)
Being as you know the city's sewer line is on the South side of the house, you should be able to locate this line with something like my tool and then find (hopefully) a "combination" clean-out just outside the wall of the home. Good Luck, David

I sincerely doubt there's any sort of clean-out on the outside of the home...I've lived here for 15 years, mow the lawn fairly regularly, have never seen any opening for a clean-out in the yard outside the home.

Now, if you mean that there would be a clean-out buried somewhere, well, maybe, but would any self-respecting plumber install a clean-out and bury it? I've seen the type of clean-outs that I'd be looking for, the one on my Kansas home sticks up about 2" above ground level, and the others I've seen stick up much further, maybe as much as 5" or 6". Nothing like either in my yard, sadly.

Another update, I finally got the RR cable to make the correct turn at the vent pipe, got all 75' of the cable into the sewer line and it came out clean. The line is still plugged, there is water standing about 1" below the toilet flange in the restroom on the SW corner. I've started hacksawing away at that stripped out hold-down bolt on the other toilet, will get it off sometime today with any luck. After that, I'll see what I can find by trying to go out the home from the other toilet with the RR....the saga continues :( .

Onward through the fog.

Dugly :cool:

YerDugliness 01-26-2010 04:13 PM

Problem resolved!
Well, the issue has been resolved. Turned out to be the city's responsibility as it related to the manner in which the city's main sewer line was joined by my main drain.

To answer my own question, I suspect that the answer to my posted question is "no" the end, we did find where the main line exited the house, it was alone neither the west side nor the east side, it actually exited the house along the south wall about 6' west of the southeast corner.

IMHO, though, there was something I learned from the vent line....keep in mind there was only one 4" did turn out to be at the point furtherest from the point where my main line entered the city's sewer line. Perhaps when a plumbing system is designed, the vents are placed at the far point from the point of termination (which in this case happens to be the city's sewer line). It might not have identified where the main line exited the house, but if I am right in that the vent is located at the furtherest point, then by deduction you can reasonably assume that the main line would exit closer to the restroom without the vent. Now, just where that might be, well, that will obviously take some exploration (it SURE wasn't where I expected it to be).

Oh, and to add insult to injury, we DID find a cleanout, and it WAS buried.....I've lived in this house for 15 years, have never had any need to know where the cleanout was located, but have mowed and weed-eaten over the location of that cleanout for all 15 years and NEVER saw it :censored: .

The :jester: plumber who did that should be ashamed of himself......IMHO!

You can read all about the last half of the saga here:

Dugly :)

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