I have purchased two Bristan Renaissance basin taps containing one black rubber washer each. The Bristan instructions say to put the rubber washer underneath the sink followed by the brass nut. I have always put the rubber washer underneath the tap and on top of the basin. Any suggestions of the best way to fasten the taps to the basin? Should I use the washer under the tap and use a little silicone just under the tap above the sink to stop surface water running under the tap and down the tail threads, or just use the washer as instructed and nothing else?