Hi Iam trying to fit a new siphon but after fitting every thing back together i have a leak under the cistern it looks like it is coming from where the siphon is fitted thro the cistern, the rubber ring in on the inside as required and is tight . i had this problem with the old siphon and had to seal all round the cistern to stop it . on the instructions for the siphon there is a flushpipe sealing washer and coupling nut but there is nothing for the coupling nut to fit to ? should i have a bit of pipe there ? it is a close coupled cistern. and i have fitted the doughnut would it help if i fitted a rubber washer both sides of the siphon ? thanks for any help. John could it be the wrong doughnut can it leak past it ?