I've just noticed my budget barrel, which contains my most recent beer, has got a dripping tap when fully closed

. If I leave it too long I'll loose the precious nectar

I saw a puddle for the first time yesterday, but thought nothing of it as I'd taken a crafty test slurp and assumed a spillage. Strange how I didn't spot a spillage earlier. The ground in my outhouse is not 100% flat, would this make a difference?
The barrel is secondhand but I tested the pressure etc before using it.
What should I do??? I have an empty king keg I could transfer it to.. any advice for how to do this without problems... will I need to reprime?