Waste Tank Vent?

Anyone know the location of the Waste tank vent (if any ) on, in particular, the Mk7 Duetto?
Our sink is very slow to empty especially when the drain tap is shut and this would seem indicate
that the tank is being pressurised by the incomming water. Cloakroom basin is ok as it starts off with
a verticle drop but the drain on the main sink is at right angles to the bowl bottom.
All the pipe runs seem to have some slight dip in them where a liquid block could occur, good for keeping smells out but a restriction to waste flow!
frederic

frederic wrote:Anyone know the location of the Waste tank vent (if any ) on, in particular, the Mk7 Duetto?
Our sink is very slow to empty especially when the drain tap is shut and this would seem indicate
that the tank is being pressurised by the incomming water. Cloakroom basin is ok as it starts off with
a verticle drop but the drain on the main sink is at right angles to the bowl bottom.
All the pipe runs seem to have some slight dip in them where a liquid block could occur, good for keeping smells out but a restriction to waste flow!
frederic

It sounds more than likely that it's a restriction in the pipe if one sink works ok the other should.

Alf

Try pouring something down the sink with the tank emptying tap open.

Paul

I seem to recall  our 95 Duetto had two  breather pipes on the top of the tank. I could just see them from underneath but really needed the tank dropping to get at them.
Our Rienza is slow to empty the kitchen sink unless you take one of the plugs out of the shower tray. I must get under the van to see what the pipe run is like. Three drains in the shower, bathroom sink drain and kitchen sink drain must mean a few pipes under there.