Hi everyone. Fairly new inspector here and I’ve learned a lot on these forums. I inspected a home yesterday, originally built in 1900 with a couple of small additions since then. It had a metal roof with zero penetrations. There are no gas appliances so that makes sense but I’ve never seen a home without plumbing vents through the roof. There’s no access to the original attic, only to a small attic over one of the additions. Could the plumbing be vented into the fireplace chimneys? Anybody had experience with this? Any feedback is appreciated!
well it better not be vented into the chimney…Did You notice any air admittance valves ?. I see these often on re-pipes of older homes…
I had the same thought about the chimney. Saw 1 AAV in a bathroom. Not one in the other bathroom or kitchen.
They could have left them terminated in the attic, again no good. I would mention the that I was unable to determine proper venting of the system and move on…
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…and don’t forget “further evaluation by a licensed plumber.”… 
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Thanks guys. That’s where I am now…I can’t confirm that it’s correct and further evaluation is needed. This is the oldest home I’ve done so just wanted to be sure I didn’t overlook something stupid!
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No “stupid” questions here Scott. Can’t say the same for answers though… 
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There should have been at least one penetration through the roof for a plumbing vent. The roofers may have decided that they were not going to spend time on vents and just left them open in the attic space under the new roof.
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There may have been a plumbing vent on the outside wall as is seen often around here.
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Thanks Larry and Alan. I don’t think I missed one in the only attic I could access and I looked pretty close at the walls for an unexplained penetration. Maybe I just missed something. I hate not having an answer but I got stumped on this one. Appreciate the input!
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By now it has been painted to match the house several times… 
That makes me feel better. Thanks 
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There may be no plumbing vents. If the fixtures are working properly no need to look any further. Maybe just make a note in your report about the lack of vent.
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Protrusion or terminations.
Plumbing Vent Distances & Routing Codes
1: Flush toilets and listen to sink drains for trap seal noise, gurgling sounds.
2: a. Run the bathroom sink and tub faucets, plug the drains with stoppers and partly fill the basins. b. Flush the toilet, pull out the stopper and see if the basins drain effectively.
When the vent termination can not be located, the observation falls under “Plumbing vent termination Limitations.” Could not locate.
Refer to the vender for location.
Recommend a licensed plumbing contract or locate the main vent.
If/when drains are impeded, require an evaluation by a licensed plumbing contractor.
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Modern homes need at least one thru the roof. Older homes you need to hunt it down to make sure it is not venting in the crawl or attic. @lkage Had it right about the outside which was very typical during certain era’s.
When I see one outside of an older home and everything is draining well, I let it go. I always call out no visible vent, vent in crawl or attic. Some other inspectors always call out the outside vents.
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Everything drained fine and there were attic and crawl areas I couldn’t get into. Maybe there was something there. For my education, what do they look like coming through a wall? Just a piece of pipe? If anyone has a picture, I’d love to see one. Thanks again!
One other thing that may be helpful. When I was just starting out, ventilation was easy for me to miss. I made a personal check-list.
Plumbing vents
Dryer vent
Bathroom exhaust
Roof ventilation
Crawlspace ventilation
Furnace ventilation
Water heater ventilation
Fireplace/chimney
Fresh air-make up
Range hood/down draft
I also use a styles and materials checklist- it is two pages and I complete it before I leave. My vents are on it as well as many other things.
If I missed a vent, I hope someone will chime in.
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That’s a great idea Brian. I can definitely incorporate that list into my Styles and Materials section. Thanks!
Yes a 3" or 4" inch terminal.
P3103.5 Location of vent terminal. An open vent terminal from a drainage system shall not be located less than 4 feet (1219 mm) directly beneath any door, openable window, or other air intake opening of the building or of an adjacent building, nor shall any such vent terminal 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.
Usually, they ended below the soffit and were better hidden:
