Once you have detected a pinhole leak in your copper pipe, and it is above the slab it is not that hard to repair. Isolate the leak, and turn the water off to the house, either at the valve where it comes in or at the water meter by the street.If you turn it off at the house then open the hose bib that is usually located just above the water shut off. This will releive any pressure from the internal pipes, and the leak should stop dripping. The next thing you need is to get the parts to stop the leak. If it is a pinhole leak all you need is a small piece of soft rubber, and a pipe clamp. Try to find a clamp that is close to the size of the pipe. You can usually find these at the local hardware or auto parts store. Make sure the rubber is soft so it will close the leak when you tighten the clamp. Do NOT over tighten the clamp or you may crush the pipe and have a bigger leak. Believe me I have done this. Place the rubber over the hole and secure the clamp. When you think you have it tight enough turn the water back on and check the leak. If it has stopped dripping then you are done and you are now a plumber. If not slowly tighten the clamp until the leak stops. Remember do NOT over tighten the clamp. In this case a little is better than too much. Hopefully this will be the last leak you will have, but chances are it will not be. If you live in [City] we can help you more. But now you know how to repair above the slab pinhole leaks.