Thursday, September 10, 2009

Smoke Test for Plumbing Leaks, Anybody know a Plumber who Smokes?

As I have mentioned so many times before the most well read of my blogs and the ones that produce the most comments and questions are the ones about “What is that Smell?”. Face it guys we all are capable of producing some pretty bad smells in the bathroom but a little air freshener and a few minutes that goes away. The kids giggle, your wife complains and maybe the neighbors threaten to move. I Have no wife and the kids are grown so my little dog “Nate” is the victim in my house. If I head for the bathroom he starts running madly around the house and across the furniture. The smell that aggravates us all, though, is the mysterious “sewer” smell that we just cant trace. I have talked about dry “P” traps, iron sulfide from bad anodes in the water heater, bacteria in the well, broken drains outside allowing water to pool against a basement wall and the list goes on and on. But there are still more examples that show up every day on a forum somewhere and some are just down right stubborn. There is one working its way through one of my favorite sites now that we still don’t have the final answer but thought you would like to see the progression and frustration that people go through trying to track the source of an annoying and embarrassing smell.
Here is the initial thread: “ We have a sewer smell from under sink and adjoining closet, but not from drains? We recently moved into a three year old house, which had been vacant for six months. We've started noticing a strong sewer smell from the cabinet beneath one of the bathroom sinks, and also slightly noticeable in the adjoining closet. The smell doesn't appear to be coming from the actual drain (the sink smells fine) and all drains are draining fine. I wiped down the cabinet beneath the sink with a disinfectant and poured some bleach down the drain for good measure, and after a couple of days the smell had gone. Today, the lawn sprinklers ran and it came back very strongly. I haven't yet been able to verify if it's present when it rains. However, our sprinklers use the same water supply as the house, and don't create any kind of sulfurous odor so I'm not positive this isn't just a coincidence. This is a downstairs bathroom, and I don't see any vent connection directly on this pipe beneath the sink. Any suggestions as to how I should go about troubleshooting or fixing this? Im really not looking forward to the prospect of having our house torn apart to track this down since we only just moved in”.


First response: Sounds like you may have a leak in a drain pipe. Is this downstairs bathroom over a crawlspace or basement where you could look around see evidence of a leak?


Thread continues: Unfortunately it's not. As far as I know, the house sits on a one piece concrete slab. This room is against an exterior wall. If it's relevant, the house is wood framed, stucco exterior and is essentially single-storey but with a bonus room and bathroom upstairs. ”


Second response: If there is a floor drain in the bathroom the trap could be dry, also if there is a toilet the seal could be leaking gas but not water unless there is back presure. Resetting it could solve the problem.


Another question: Just to make sure we haven't missed anything simple: Are you sure there isn't a failed AAV/mechanical/cheater vent under the sink? I recently experienced this problem. Before I figured it out it, the smell was worse some days compared to others for reasons I never figured out.


Thread continues: There is one of these in that bathroom but it's under the other sink (two sinks, one on each side of the room). The one with the mechanical vent doesn't smell at all, although I noticed today it drains a bit slower than the one with a 'real' vent. Any way to test these cheater vents? I know if they stick open they will smell horrible, but I'm wondering if this one could be stuck closed or not opening properly.Had some different plumbers out today, the and thought that a joint in the vent pipe right before where it exits the roof was to blame. I'm not totally convinced yet (the joints looked pretty good after it was removed) but it's hard to tell, it's been dry and the smell has almost gone on it's own. I did run that sprinkler zone for an hour today to try and get the smell to come back, but it didn't. So perhaps it's not linked to wet ground after all. I'm desparately hoping this will have solved it and that no slab work is required, but I guess I won't know until it next rains heavily. Thanks for all the advice, it's much appreciated.


The next response: We currently have the same problem and as we recently had a plumber here twice fixing leaks and replacing toilets, I knew it wasn't in the house. I decided it was time to call the City's Public Works Dept. (we're still waiting for them to arrive). One of my neighbors just had a sewer back-up problem and had to move out for a week while floors were ripped out and pipes, flooring etc. were replaced. We have this added coverage on our insurance and hope you do too. I'll let you know how it turns out.


Thread continues: Thanks for the info, there's a floor drain in the shower, but it gets regular use (2x a day) so I don't think the trap is dry. We recently had a blocked toiled drain that wasn't solvable by plunging or chemicals, and called a plumber out. There isn't a close by cleanout so he removed the toilet to snake through there. He did fit a new wax gasket to it, and surprisingly the smell is barely noticeable in the water closet, which adjoins the sink cabinet. Some more information: It rained heavily today, and the odor has got worse. It's now noticeable throughout the whole house. I also noticed the ground seemed more damp outside the affected area. I removed a plastic trim/sealing ring from where the sink drain exits the back of the cabinet, and the odor seems to be coming from there. There is a roof vent right above this area, but it appears to be clear. I was able to lower a length of hosepipe into it, and when the toilet is flushed/faucet is run I hear water clearly through it.

Next response: (Are we getting close yet?) Based on the above, is it fairly safe to assume it's a cracked or leaking pipe somewhere in the wall or below the floor? If so, any ideas what should I expect as far as getting it repaired?

And then a break through?: I've pulled out some more fiberglass insulation from the wall behind the sink today, and here's what I saw: (dimensions are approximate)The 2" vent pipe enters an open 4" pipe just above floor level. It's pressed against one side, and has pieces of wood wedging it in place on the other side. There's not very much gap between the inner pipe and the outer pipe, but there is some. I dropped a shop-vac hose down there so it was resting on the lip of the 4" pipe, and turned it on for a couple of seconds. Then I disconnected the hose from the shop vac and could definitely smell the odor from it. Repeated this 3 or 4 times to verify, and got the same result each time. So I'm fairly sure the smell is escaping from the gap where the smaller pipe exits the larger one, which is probably bad. What would my next step be? I know from here on out it could get hideously expensive if they have to start digging up the floor. They've mentioned cameras etc. but I'm wondering if there's any specialist equipment (gas analyzer?) that I should specifically be asking for.

Response: If the 2" vent pipe is vertical and goes into the 4" pipe then it appears you have found your problem. If it were a horizontal run I would expect you would have noticed water leakage. Without a picture (although a good description) I would say you have sewer gases escaping from the gap between the 2" and 4" piping. Depending on what type pipe(s) you have there you should be able to connect the two together with a "Fernco" style coupling that fits each size pipe.
AND
You're saying the 2" and the 4" pipes dont make a solid connection???? Let me get my head to stop spinning.....The 2" enters an open end of the 4" and is just wedged in there? Whomever did that should be beaten severely about the head and shoulders with a dirty sock pulled out of a clogged toilet.
AND
This was the same as my initial reaction to his statement, but I felt he had enough troubles already. "as the home owner stated that he has already had "plumbers" out to investigate this problem and they had not found it, the homeowner found what appears to be the problem. Hopefully the homeowner is an adept DIY and can fit some type of coupling onto these two pipes. I am not recommending this, but at this time duct tape would be an alternative to what he has

Thread continues: Sorry guys, I didn't explain that part very clearly. As best we can tell, the 4" pipe isn't actually 'used' in the drain system, although it appears to be drain pipe it's acting more as a conduit from what I can see. I know the house is built on a concrete slab, although I'm not familiar enough with building practices here to know whether or not all the plumbing is encased in concrete, or whether it sits in the dirt below the slab. If it's the latter, this 4" piece of pipe seems like it's set into the concrete, and the 2" pipe just passes through it. Both pipes are set vertically. At least I hope this is what's going on. The smell has been gradually fading over this past few days, but it hasn't rained at all which could explain it. With that said, the source of the odor did appear to be the gap between the pipes. My hope is that it was just residual but I guess we'll see once it rains heavily again.

Now to find a plumber who smokes? Or maybe one with a can of spray foam?Duct tape?: The quickest way to detect the leak is to smoke test the drain line from just outside your house. I know that sounds like a big deal but it's actually very simple IF you know where your clean-out fitting is outside the house. Any big box hardware store will have the non-toxic smoke packs. You blow the smoke with a small fan into the clean-out fitting (make sure and plug the "downstream" side of the line, and the smoke will show up at any leaks in the vent pipes. The smoke is very dense and will show up if there is a cracked pipe, etc. Just make sure and plug the downstream (or street side) of the drain line before testing. Also, probably unlikely, but you might first call your water/sewer company and see if they will come out and smoke test the line for you. Most places won't but I've encountered some companies will. Yet another opinion: I'm not aware of any "easy" test that you can conduct to confirm a leak. (the smoke test will confirm you have leak somewhere, but not pinpoint it if smoke shows up in that sleeve). A "hard" test would be to isolate the line (somehow plug it on both ends, don't know if that's possible, and probably not practical) and pressure test it with air or water. If it won't hold a constant pressure then you definitely have a leak


Well I guess you can get the picture? Short of breaking concrete, tearing out sheetrock and studs and going through multiple plumbers along with several of us well meaning forum contributors, some smells just can’t be found easily. I suspect the smoke test will show the problem to be a leak in that drain line, The mystery continues and Ill keep you informed as the thread continues.

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