Are the waste pipes vented properly?

Depending on the layout, seems like the pipes could be venting up through the drains in that bathroom and causing a smell - if for example the normal vent pipe is blocked or improperly installed.

Yes, fair question.

1. In that case, wouldn't the 5 floors below not also complain about the same? Or is that something that I would feel heavier on the top floor because the gases move upwards?

2. No way to check this myself I suppose? How would one go about this - a professional to check from the roof?

Sounds like the venting is clogged our closed off.

Try keeping the underflor siphon wet - I imagine it is for water from floor-cleaning etc? Those siphons just tend to smell bad, if they dry up.

I remember working in an office-space where some old guy watered the floor-siphon in one of the bathrooms on a weekly basis to prevent it from smelling like shit.

I am no expert here at all, so hopefully someone with more experience will chime in. However my guess would be:

1 - Depending on the venting system in place, but yeah you could be the worst affected as you suggest. 2 - I would think that checking the roof / the top of the vent pipe for environmental blockages, caused by animals or plants, would be a good idea

Again, I'm guessing here.

I think this comment is on the right track. Methane is lighter than air. A break or fault in the vent stack in the floor below would tend to rise.

I remember staying in a hotel in Oaxaca Mexico. Nice place but the floor drains lacked traps. I think they put a trap under the toilet but however they tied in the floor drains it bypassed that trap. The shower area always stank just a little bit. So you could be looking at a design flaw.

Or, there can be a penetration in the vent stack-- Crack, loose joint, nail hole.

I know of two methods to assess. One is a smoke test. Basically they open a clean out down low and pump smoke in it. Wherever the smoke comes out needs to be repaired

The other is by using a boroscope inspection camera. You can drop it down from the roof or anywhere there's a clean out and just inspect all the joints.

So I would ask around for plumbers that are familiar with these techniques. My first choice would probably be the smoke test.

Is there a gas trap under the sink? I had a similar problem recently that was solved by pouring some bleach down the drain of the sink and shower. It ended up being stuff built up in the sink drain. Seemed so simple afterwards.

Adding to the ventilation hypothesis. The following is a look downwards from the bathroom window.

Here is what I see:

• The pipe on the right is gas.
• Looking down, I see that all bathrooms have their individual ventilation, correct? So they would not have the same problem.
• The pipe on the left appears to emerge from my bathroom. Is that the ventilation pipe headed to the roof? I’ll go there now to check it out.

https://abload.de/img/87922e5a-5f57-4ac5-bqce47.jpeg

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Update

This is the exterior view of the bathroom (the left window). It looks to me as if the pipe on the right hand side of that window emerges from that bathroom, then moves up and ends in an inverted U.

The pipe on the left that also crosses horizontally is gas and can be ignored.

All bathrooms below seem to have their own ventilation.

So most likely that pipe deserves some checking?

Have you checked if any of the siphons in the drains are being sucked dry? Under-pressure in the drain pipes (due to blocked vents or bad design) can suck the water out of the siphons essentially allowing the air from the sewer to vent directly into the room? Would typically occur when other apartments down stream flush water through the system.

How does this look to you? This image from outside show the bathroom, I assume the vertical pipe is my vent pipe and might be blocked somewhere?

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https://abload.de/img/complete_viewyudx5.jpg

The underfloor siphon actually is for the toilet (and I think the shower and sink also go through there). Meaning "it is located underfloor".

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So:

• Sink: Has a siphon directly underneath, then feeds into the underfloor one.
• Show: Assume the same.
• Toilet: Directly into the underfloor one.

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All of these look alright (have water in them, plumber also didn't see anything odd when opening the underfloor one).

Your HVAC system could be putting that smell in there. Check for that also. It can draw the gases into the ducting and blow it back out.
Had that in one house, one bathroom smelled, off and on. Tried several different things. Even did a smoke test and nothing. Ended up finding a vent pipe going into a cold air return that had a joint wasn't glued by the plumber. Only way I found it was by removing the cold air covering and pulling on the pipes.
Another is possible the toilet seal has failed. Next, look for anything that was added recently. A screw/nail could have went through a pipe.

Is the smell like urine or sewer vent?? We had to regrout the tiles on a mosaic floor to cover urine smell coming through the floor. Worked like a charm.

It's sewer smell, good thinking though!

Weird, I could have sworn that I had responded here already. Anyway:

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Could you speak a bit more about the seal? If I assume that the underfloor siphon and ventilation work, then the portion of the pipe that could be affected by a leak in the seal would only contain a limited amount of smelly air, right?

This toilet is stepped on regularly, for example to turn off the gas outside. I also did install a new toilet seat, which doesn't involve drilling, but a fair bit of shaking and movement - could these things have unsettled a seal?

The only bathroom that I ever encountered with a septic smell was because the wax ring under the toilet was defective. They are cheap so just change that and reseat that toilet.

Then, figure out a way to reach that gas valve without stepping on the toilet. A folding step ladder for example.

Wax ring is an American thing, we don't have them in Europe at least not as s standard thing. We use large diameter PVC couplers with rubber gaskets for connection between toilet and floor pipe.

Yeah I looked again at my toilet here - it flushes to the rear (but stands on the floor - so not a proper hanging toilet either), and there are multiple PCV pipes / couplers that go into the wall. All quite crusty and old.

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Removing that toilet and redoing the PVC portion is more than I would endeavor, but I suppose that this is what the plumber had in mind.

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Any intermediary solutions, such as drowning it in Silicone?

Or will that not work on PVC anyway?

Man, just start looking for a new place. you don't own this.

But I like it :)

Put a smoke tablet in your drain and see where the smoke goes.. -plumber ( the tablets are like 3 bucks)

Trap for sink leaking so its empty?

If you like the smell, then what's the problem?

I lived in an apartment in Italy that had the same problem, one bathroom that stunk like a sewer. But it was only bad for a few months of the year, in the summer I think. We talked to other people who lived in different buildings in same city that had similar problems but everyone just shrugged and chalked it up to poor infrastructure. We moved, but even in this house we are in now, the plumbing stinks in the summer. We just close all the drains when not in use. It isn't that bad in this house. It's gross though but people here seem used to it!

Had a similar issue and for me it was that the vent was cracked inside the wall, leaking sewer gas into the living space.

Drain and sewer cleaner here. In a situation like this my company would perform a smoke test. Access the sewer line and pump smoke in which would reveal where it can escape. Sometimes it's a tiny gap in pvc glue at a hub or a tiny crack in cast. Sometimes there's no smoke and instead a mouse died in the walls. Chasing smells is tough without smoke. Another reason can be if the fixtures are not used frequently the traps dry out and smell quite bad. Running hot water to see if the smell is more noticable can help isolate it to sewer lines as well.

Don’t seal yet. I would do a smoke test; that is, if they are available in Spain. Essentially banana ( or other scented) harmless smoke dropped in your vent pipe. We call them stink pipes on roof. You’ll know immediately where the sewer gas leak is coming from. Just did this myself recently and immediately saw smoke coming out of the wall as well as from under toilet. Re-seating toilet was easy, but also had to tear up wall. Found that only one side of vent pipe was capped and the other was wide open. That t can sometimes pop off or get knocked off when snaking the line. I tried literally everything before this fix. 3 plumbers just scratched their heads. They were all sure it was a dry ptrap. Did the bleach, vegetable oil, calking etc. I would say that if the sewer gas smell is big, then your problem is most likely big as well. Good luck.

If you’ve got a bathroom fan, get a look at the damper in the line. If it is not sealing when not in use, it may be the cause of your problem.

Just remodeled. Got a brand spanking new bath fan & the damper wasn’t tight. Bathroom smelled like a musty attic & was 20 degrees warmer in the summer until I installed an aftermarket damper. I don’t know if it is a design flaw in the fan or my contractor just got a bad one.

It may seem silly but if you have a shower curtain check it for mold or slime at the seams. Believe it or not it can make your bathroom smell like cat pee.

I second this. Try filling all drains and pipes with water. Grab pitchers, fill them up, and empty them down the drains, you may need to do this every few weeks as the water evaporates out of the pipes.

If for some reason you only have straight pipes down to a source you can't get to, try installing P traps if you can so water keeps the air from the sewers from coming up your pipes/drains and into your bathroom.

The toilet is not a ladder.

Thanks, that sounds like a doable approach.

The plumber came yesterday night and sealed the rear of the toilet with bitumen/ asphalt - so far it seems to work, but it is also a little too early to tell since the sewer smell might be hidden behind the asphalt smell right now.

I asked about the vent pipe - he said that pipe is there to allow air to enter the pipes, not to leave the pipes. And since there are no issues with anything being sucked dry, it seems to work fine.

Will see if it the sealing already works, and if not, the smoke test sounds good.

Thanks! Plumber came last night and sealed around the PVC tubing, if that doesn't work I will push for either him to do a smoke test or find someone who will.