I am having a lot of trouble fixing a dripping kitgen mixer tap. The washers that I have fitted are the correct size and are fine when fitted but after a couple of days the tap starts dripping again. It's a Bristan tap and the seatings inside look good. The trouble is that the washers just seem to go quite squashy and move about after a while and this is when the drips start again. When they are taken out you can see that some of the contact rings are off centre. Does anyone know if it's poss to get washers in a harder rubber? I don't think our high water pressure helps but then some of the previous washers have worked fine for years.