Adding GFCI protection.
Q Our old house has an outlet on each side of the kitchen sink (on the same circuit) and we want to protect them with a GFCI. Can we install one GFCI outlet to protect both of them?
K. McMahon, via e-mail
A The answer is sometimes, but unless you have a pretty good familiarity with electrical wiring, using a single GFCI is probably not worth the effort.
A GFCI (ground fault circuit interrupter) is a shock prevention device that's required by the National Electrical Code in certain outlets, including kitchen counter outlets. Older homes built before code requirements went into effect usually won't have them. But it's a good idea to add them, as you're doing.
A single GFCI receptacle can protect additional standard outlets if the power flows to those outlets through the GFCI, that is, if the GFCI is "upstream" of the outlets. (See photo.) In your case, the challenge is to figure out if both receptacles are on the same circuit (easy) and which one, if either, is upstream of the other (complicated).
We recommend that you avoid unnecessary complexity. GFCIs only cost about $8 each. Simply replace both outlets with GFCI receptacles. Remember to check the electrical box sizes when you do this and to upgrade any box that's too small. (See "Install a Dimmer Switch," June '04, p. 101, for details. To order a copy, see p. 7.)