John 2000

G, Hi.

The idea of the vents is to stop back pressure forming
in your pipe system underground.
It helps to stop waste water blowing back up the pipe
and help to stop smells coming from bathrooms/washbasins
normaly you do not smell anything because under the sink
and behind/under the toilet there is a pipe in the shape
of an S or a P this traps a little water and stops bad air
comming into the house, if you did not have the vent your
toilet would bubble and plop giving of a very very bad smell.
Keep your vents open,

John 2000