"Harv" wrote in message
...


Don't use an air admittance valve. Put an inspection cap above the
toilet
on the stack. I assume the basin is pied into this stack around where
the
wc is connected to the stack. You only need to use a Hepworth HepVo
trap
on the basin, nothing else.

See the web site:
http://www.hepworthplumbing.co.uk/hepv1.htm


Just had another thought, what of the sink is full of water when the
toilet
is flushed, or the bath emptied, or next door does one of the above, won't
syphonage occur, and bad smells come up through the syphoned trap?

It is always best to have two on the system, as the probability of both
basins being full is remote. If installing the air admittance valve is not
a problem, then fit both.




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