How can I stop a leak from the pipe that comes out of the wall under the to?

If the tap has been left (fully) turned on for some length of time, its possible it may have partially seized and if it was difficult to turn off, you may have damaged the rubber seal inside thereby causing it to leak. you should not leave the tap fully on, but turn it back a half or 1 turn to prevent this happening again, and occasionally turn it on/off to prevent it seizing again. the rubber washer will probably have to be replaced

c,jenkins
February 2008