In article ,
Jethro writes:
On Jan 25, 5:52*pm, (Andrew Gabriel)
wrote:

I'm struggling to imagine what you're using. In pictures of a
Floplast, I can't see any AAV mechanism, but maybe it's hidden
inside?

I found a picture of the AAV's I usehttp://www.askmehelpdesk.com/attachments/a/12211d1221468609-air-admit...
There is a moving part in the AAV, which is the one-way air valve
diaphram with a post on the bottom to keep it in place. The post
sticks out of the bottom of the AAV, and you can see it move up
when the valve is sucked open by a vacuum in the pipe.

If the diaphram is missing, then there is no valve and the sewer
pipe will be open to the room. You can unscrew the top of the AAV
and see if the guts are missing.

it's similar, but it lacks the little bit coming off the horizontal
outlet.

Well, that is the AAV. Without that, it's just a bottle trap.

However, compared to the one I took off, it has a hollow tube
*inside* where the water sits. No valves, no moving parts. I really
haven't applied any brainpower, or dusted off my A level physics to
work out what's going on ... I just wanted it to work. That said, I
have taken it off, and put the old one back. Assuming there's no smell
in the next day or two, I've isolated the problem, and will see how
it's *supposed* to work. And if I get that far I'll locate my USB
cable for the phone, and post some piccies ... my next laptop will
have bluetooth ...

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]