# Protecting multiple outlets with one GFCI; is it possible with this wiring scheme?

I have a family-room circuit with 5 outlets and a one-year-old who thinks it's funny to try to stick things in them. So I thought it would be a good idea to add GFCI protection (and tamper resistance). I know that in theory you only need one GFCI box to protect the whole circuit, the trick is to determine which receptacle is farthest upstream and replace that one, making sure you get line vs. load correct. So my plan was this: take all five boxes out of the wall, disconnect and separate the wires, flip the breaker back on, and walk around with my non-contact voltage tester looking to see which black wire still has voltage on it, implying it is the most upstream. Well, it turned out that when I did this, every single black wire at every single outlet still had voltage. I'm sure this wasn't a false positive because none of the white wires triggered the tester. I take this to mean that there is one main wire that circles the perimeter beneath the floor, and right below each outlet there must be a junction box with a separate wire going up to the receptacle. Is my reasoning correct, both regarding how to find the first receptacle and what it means that the technique didn't work? If so, does it imply that I can't protect this circuit by replacing a single receptacle, and would need to either install a new outlet farther upstream or use a GFCI breaker instead?

• How many wires are in each box? Are there wires pushed back inside the box, that are not attached to the receptacles? – Tester101 Oct 15 '15 at 13:23
• It's fairly common practice to connect receptacles using pigtails. So if you only disconnected the wires attached to the receptacle, the circuit would not be broken. Look in the back of the box, for a bundle of black wires. – Tester101 Oct 15 '15 at 13:25
• @Tester101 No pigtails or pushed-back wires. One box had two sets of wires coming in, the rest only had one. – dlf Oct 15 '15 at 13:26
• You could always protect the entire circuit, by installing a GFCI breaker. Though you'll probably also want (if you don't already have) AFCI protection as well, so you'll need a dual function circuit interrupter (DFCI). – Tester101 Oct 15 '15 at 13:30