Help finding plumbing vent stack

I am trying to locate the vent stack for my plumbing since I realised that there was no stack coming out my roof. My house is only 3 years old, and I've never had a problem with the plumbing, so l assume that it's vented into the attic. The problem is that I have 6-12 inches of blown-in cellulose insulation up there, and cannot find the vent to save my life after crawling around for 2 hours.

The guy who actually did the plumbing has moved away, so I can't either ask him where he put the vent or punch him in the face. Does anybody have any ideas as to how I can l locate the stack?

So you went in the attic and didn't see it? Usually stacks are close to your bathroom, usually within a few feet of the toilet. Sometimes they will offset in the attic though. If everything is draining ok then it couldn't be under the insulation because the insulation would choke off the vent and it would reek of sewage in the attic. Can you see it from the front or back of the house from your yard? Maybe next best thing to try if you still can't see it is if its safe to do some climb up onto your roof or get someone to do it.

You don't think there could be an AAV for the system?

If there is no open vent in the entire system it would not work. AAV will allow air in but will not allow any out. Plumbing systems can create both positive & negative pressures on a system. One of the reasons for venting is so these pressures don't exist in the DWV system.

John

I know it's not coming out the roof, myself and others have been up there. Also, the cellulose insulation is pretty light, so I can see it not obstructing the vent, but there's no smell of sewer gas in the attic. I was dumbfounded to discover this, let me tell you, as I never suspected there was anything wrong. I know it's vented somewhere.

I feel like the vent should be near one of the bathrooms, and I thought that I might have heard some gurgling down one end of the house when the washing machine was draining, but couldn't reproduce the sound by either running the tap, flushing the toilet, or getting my wife to fill and drain the bath while I was up there. Does anyone have a creative solution I might try? I wondered if I might plug most of the drains and hook up the exhaust of my shop-vac to an open one. I feel like the air should choose to go up the stack, rather than up any of the drain traps (which I don't really care about, other than the toilets). If there was insulation covering it, that would certainly reveal the stack location. Am I nuts? Alternately, I wondered if I might clear one drain trap, then put a speaker on it and play music. The sound should conduct up the piping and out the vent, right?

I know I'm probably sounding like a crazy person, but it's near freezing outside and I have 1700 square feet of attic to crawl around, plus I'm lazy. So I'm trying to get creative.

Yeah an AAV wouldn't work, not to say they didn't do it. It's just highly unlikely. I've never had an issue of not being able to find the stack I guess haha. Now your traps could blow out or siphon if the pressure is any higher than 1.5" water column which is like less than a butterfly fart. I'd suggest maybe a smoke test. Fill all the traps with water. Throw a smoke bomb down the cleanout and close it really quick. I dunno that's probably my first test I would do. I'm not sure how small of a smoke bomb you can buy but buy a few small ones. Usually when you do a smoke test you do it to test for sewer gas leaking out and cap the roof vent, however since you can't find the vent, I think that may be your best bet. Someone else may have a better idea though.

I wouldn't through a smoke bomb directly into the waste line. What we have done is to put the smoke bomb into a bucket and using a shop vac with both intake and discharge hoses. Pull the smoke out of the bucket and into waste line.

John

Not sure where to get a smoke bomb, to be honest. I live in Canada. Maybe I'll just put the lid down on the toilets, plug the drains, hook up the vacuum and hope for the best.

I'll be sure to send pictures if something explodes.

I live in Canada too Marc haha. And ok John makes a good point you could definitely do that, I've never personally done one so I only know the theory behind it. But go to a plumbing wholesaler? Got a wolseley by you or Emco? If you went there I'm pretty sure they would have them