Make a visit to your local plumbing merchant and get a roll of PTFE tape and some insulation. Wrap the tape around the threaded nozzle of the tap clockwise between twelve and fifteen times. Then re-thread the plastic coupling back on to the nozzle of the tap. This will stop the joint dripping all year round. Then use the insulation to wrap around the tap and any outside pipework to prevent the water freezing in the pipe on the coldest days.