Electrical – How to improve the wiring under the sink for a garbage disposal

electricalgarbage-disposal

My vegetable sprayer line broke yesterday, which led me underneath my sink. It wasn't until I was kneeling in a large puddle of water with the line draining on me and the floor that I realized how bad the wiring was for my garbage disposal:

Shocking finding under my sink

This obviously needs to be addressed. My question is which of the following approaches will solve my problem and won't kill the next tenant?

  • Cover the J-box with a plate that has a hole and let the romex come through
  • Wire in an outlet (half-hot) and convert the romex to a 3-prong plug
  • Wire in a GFCI outlet (half-hot) and convert the romex to a 3-prong plug
  • Something else?

Completed project:

All tidied up, likely not to kill me

Best Answer

The answer to your question depends completely on whether this node in the circuit is GFCI-protected. GFCI protection is an absolute must for your disposer; it's a high-amperage electric motor hooked up to your kitchen drain.

Since this J-box doesn't have a standard 3-prong outlet, you'll need to find another outlet on the same circuit; look for a countertop outlet nearby. Plug in an outlet tester (like the one below, available for $5-10 from your local big-box home improvement store), turn on the disposer, and hit the black button on the tester to short hot to ground, inducing a "ground fault".

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If the disposer has GFCI protection, it will cut out, and you're golden as far as circuit safety. If not, you definitely need to rewire this J-box with a GFCI outlet.

Even if the disposer is GFCI protected, you have other problems. The outlet is in a "wet" place; you hope that the under-sink area never leaks, but there is always, always, a plumbing emergency at the kitchen sink at some point. To avoid a continuous ground fault through contact with standing water in the J-box (which would prevent you from resetting the GFCI until the whole area dried out), you should seal this area as best you can. A little adhesive spray foam to fill the gap between the wall and the back of the cabinet, followed by a layer of silicone adhesive caulk to waterproof the spray foam (people think spray foam is waterproof, but it really isn't), and a child-resistant outlet and plate with a rubber or neoprene gasket (and/or another dab of silicone) should keep the water out in any situation less than a full flood.

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