How do I install a GFCI receptacle with 2 black and 3 white wires plus a ground? I have two such regular receptacles next to sinks and should replace them before the upcoming home inspection, please help. The instruction sheet for Leviton "smartlockpro" receptacle says: "do not install the GFCI receptacle in a electrical box containing (a) more than 4 wires (b) cables with more than 2 wires; contact a qualified electrician if either (a) or (b) are true"
edit> This is an existing home built in the 70s. The bathroom light appears to be the 3rd white wire. To top things off the 3rd wire seems to be on a different breaker as it becomes energized and lights up the power sensor after both blacks are switched off but not before shutting off the breaker.