i need to install a gfci outlet above my sink but the house is old and only has 2 wire system. how do i go about grounding this outlet? the house is on a slab and has no basement

 

If you only want ground-fault protection, you need no grounding wire. Just install the GFCI receptacle. It won't be grounded but it will work just fine as a GFCI.

If you require true grounding, and I don't really know why you would, then run a cable down from the attic into the wall where you want the receptacle. Run that cable through the attic to above the panel, and then down into the panel. Install a new breaker in the panel for this receptacle. Install an old-work box where you want the new receptacle. Use 12/2 cable and a 20-amp breaker. If your attic gets really hot, you might need 10/2.

Obviously there's a lot more to it than that. Get a book or two on home wiring from your public library or home improvement center. These books cover this kind of a project very well. Consider having an electrician do the work inside the panel.

 

thanks john, but is there any other way than to run a ground back to the box? the reason i need it to be grounded is to pass county code. i am going to rent the house out

 

Nope. But are you sure the requirement was for an outlet with an equipment grounding conductor? Or was it just a requirement for a GFCI outlet?