Terrible smell from bathroom but only at night?

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Fred99

13684 posts

Uber Geek

#2274367 10-Jul-2019 23:04

I can't see an AAV, but at a guess reckon it's worth putting one in.

Where the cap is on the top/left of the trap, not sure if there's enough room, but one of these:

https://www.bunnings.co.nz/aqualine-40-50mm-air-admittance-valve_p00940727

because of lack of clearance - may need to put a 90 deg elbow to fit it, or loosen off fittings so you can rotate it into place, I don't think it matters if the AAV is vertical or horizontal.

My guess is that suction from flushing the toilet is draining the shallow trap in the shower rather then the basin, but fitting an AAV under the sink should do the trick anyway.

JStew

54 posts

Master Geek

ID Verified

#2274368 10-Jul-2019 23:09

Fred99:
I can't see an AAV, but at a guess reckon it's worth putting one in.

Where the cap is on the top/left of the trap, not sure if there's enough room, but one of these:

https://www.bunnings.co.nz/aqualine-40-50mm-air-admittance-valve_p00940727

I think that cap is a AAV, looks nearly identical to this: https://www.bunnings.co.nz/aqualine-32mm-air-admittance-waste-trap_p00134622

Fred99

13684 posts

Uber Geek

#2274370 10-Jul-2019 23:24

Nope - that one's got an AAV built in - the trap you've got has a cap screwed on over where a separate AAV could be fitted.

IMO there's some problem. Either there should have been an AAV fitted because the shower/basin drains share an unvented drain to the sewer with the toilet, or there is a vent or AAV elsewhere that's not working, or some other change was made some time.

You should probably get a plumber. My suggestion was a $20 cheap fix that *might* work, with no guarantee it will, and quite possibly not legal to DIY.

JStew

54 posts

Master Geek

ID Verified

#2274745 11-Jul-2019 17:57

Alright, I think I may have worked out what's been going on and thanks everyone for your advice, you're been great! Someone on here sent me a PM yesterday saying they had the same issue and had to have their shower drain replaced. Them saying this got me thinking a little and made the most sense out of anything I had heard yet. So tonight I looked under that silver / chrome cover of the shower waste and found out that it was made by Viega (a German brand that's nearly impossible to find in NZ ....). I looked at their website and found it really hard to use and could find what I was looking for. I then searched them on YouTube and the first video that came up was a guy replacing the trap of the shower waste (the white thing I took a photo of yesterday with a couple of o-rings on it). Right at the end of the video, he showed that the trap can only go one way as there's a grove that connects to the bottom of the waste to form a proper seal.

Straight away I thought "damn, I could have been putting the trap in incorrectly after cleaning it" which would explain why this started happening suddenly. I also noticed at the end of the video that he tested the trap by pouring water into it and it held the water ... given it's a trap. Mine seems to leak very slowly and the water level in the trap decreases. Luckily there's another shower in the house with exactly the same setup, so I've grabbed the trap from that and put it in my shower. Filled it up with water and it seems to be holding the water well.

So - I'm going to wait an hour and get flushing with the toilet. Looking back, if this is in fact the problem, it all makes sense. I probably caused this 5 months ago when I cleaned the shower trap by not putting it back correctly and have been doing the same since. It also explains why it only happens at night as the shower trap slowly drains during the day and is empty by the time I get home. However yesterday I did flush the toilet at 4:30pm or there abouts and the smell wasn't that bad, so it doesn't 100% explain why it was happening. Anyway, will know in the next few days whether I've nailed it but it seems like the most logical cause so far.

Hey one thing - the AAV under my sink, I cannot for the life of me work out how this thing works. Some photos of the parts and then the middle of the AAV are below. From what I can tell the blue disc seals the pipe and then the white cap screws down and pushes the blue cap onto the pipe pretty tight. As a general question, I'm wonder how this lets air in, because it looks like it can't? My kitchen sink also has exactly the same AAV on it too.

White cap that sits on top of the AAV and then the blue disc under the cap:

Blue disc sitting on top of the AAV (white cap screws over the top):

Nipple / washer sitting in the middle of the AAV:

Middle of the AAV:

JStew

54 posts

Master Geek

ID Verified

#2274747 11-Jul-2019 18:00

Ignore my question about the AAV! I just realised that it pulls air through from the bottom of the AAV, not where the blue disc / cap is. Makes a lot of sense now :)

mdf

3512 posts

Uber Geek

Trusted

#2274752 11-Jul-2019 18:18

Variations in smell might just be due to what your upstream neighbours had for dinner that night.

Good luck, hope you've cracked it!

mclean

581 posts

Ultimate Geek

Subscriber

#2274762 11-Jul-2019 18:27

Incidentally, the small vent built into the basin trap is known as a "trap vent". Not strictly an AAV under the plumbing rules - you shouldn't use them in place of properly sized AAV's or vent pipes. Not under the current rules anyway. I'm not sure but I think they're supposed to make the basin drain nicely (ie quietly).

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