Hi

The waste outlet from the P-trap in our new WC (believed European), has 2
sharp ridges along the outside. The ridges stick out about 3mm and run
parallel to the axis of the outlet. The ridges will prevent a standard
connector from forming a seal around the outside of the pipe.

The supplier said we need a 'double suction' connector but I've never heard
of this any can't find any reference to such a thing.

The inside of the outlet is smooth, so I suspect some sort of connector
which seals against the internal wall is needed, though I guess this would
not make for a smooth flow.

Can anyone shed any light on this?

Cheers

Steve