The tap washers are not responsible for water leaks, I'm afraid. Unfortunately the only way without seeing it is to remove the tap nut connectors, these are under the sink and the last brass nut which connects the copper to the tap, inside their there are fibre washers and these are most often the problem, something you might try is if the water is running down the tap and onto the basin, or when using the basin excess water is flowing between the tap and where the tap goes through the basin, hope this is of some use to you, however I think you are going to have to call somebody in. Good Luck.
Dave C, February 2008