Existing bath has developed small leak (probably been there for some time) which I found to be from the fitment under the waste hole which operates the pop-up plug. Removed it and cleaned it but curiously there seemed to be no washers involved. Might this be the reason for the leak? The fitment under the bath is a female fitting about 60mm id; it is clamped onto a raised collar which is part of the drain fitted to the bath itself. Unless this arrangement is intended to seal just by making it very tight, I would have thought there should be a washer there. Anyone familiar with this type of fitting (make unknown) and could advise please?