Electricians: how to ground an outlet in an old house

I’m going to install a new garbage disposal for my mother-in-law, whose house was built in the mid-1950s; many of its outlets are not grounded. But I plan to use this remote control switch, which I strongly suspect needs to be plugged into a grounded outlet.

The existing disposal has a magnetic switch in the stopper (I’d never seen one of these before), so there’s no wall switch to connect the new one to. Also, most disposals now come with plugs, instead of being hardwired, as the existing one is. However, as it happens, there is a switch under the sink that my wife’s grandfather installed to shut off power to the adjacent dishwasher. He did that to prevent small kids from playing with the buttons on the then-novel dishwasher. That function is no longer necessary, so my plan is to replace the switch with an outlet. The remote switch controller will plug into the outlet, and the disposal will plug into the controller.

The romex feeding the switch box has a ground wire in it, but I’m not sure that it is really grounded. I don’t have my tool bag with me, so no ground tester is available (unless I go buy one). So my questions for Doper electricians are:

  1. Is there a way to check whether these wires are grounded without a tester?

  2. If it’s not already grounded, how can I safely ground this box? Can I run a single solid wire to a nearby pipe, and if so, how do I attach it securely?

  3. Should I install a GFCI outlet? It seems unnecessary, since the remote switch will isolate the user from any direct contact with the circuit.

  4. My Plan B, which would in many ways be much simpler, is to cut off the disposal’s plug and wire it into the existing switch (rewiring the disposal so it’s not switched). However, I suspect this is not to code. Am I right? (We’re in Massachusetts, if that makes a difference.)

FYI, the brand/type of disposal I’m looking at does not seem to be available with a hard-wired option, nor is it available as batch feed (switch built in to the stopper.) So those are not viable alternatives.

Any other advice or suggestions? I need an answer relatively fast: the hardware arrives on Friday. Thanks.

So you have a number of issues here:

  1. You need some kind of tester here or a simple lamp. If you can connect the lamp to hot and ground, it should light up properly. If it is dimmer than when plugged in normally (Hot/neutral) then the ground is not good.
    2.This does not provide a good ground, unless the pipes are bonded together with the neutral at the panel. The point of the ground is to have a path for current to safely travel, causing the breaker to trip or the fuse to blow.
  2. A GFCI is an acceptable alternative to a ground and would prevent the steel sink from becoming electrically hot in a fault condition. I would do this for sure.
  3. Not in Mass or an electrician, but generally speaking cutting off a cord will violate the UL listing of the appliance and kill your warranty.

I’d also like to point out that the switch you have chosen with the slogan “To build beauty of life with heart” is almost definitely NOT UL listed.

What about something like this:

if it was built in the '50s, and has cabling with a safety ground wire, and the wiring is run through metal conduit and boxes, the ground might be attached to the box.

you could use a multimeter and check the voltage between hot-neutral and hot-ground wire. if there’s no voltage between hot-ground then the ground wire is not connected to anything.

Despite their dubious command of English, according to the manufacturer, it is.

I was looking at those air switches, but because I don’t have the tools (or inclination, even if I had the tools) to drill a hole in the counter for it, we’d have to sacrifice the soap dispenser, and at that, I think installing it at the back of the sink would be a pain. So this battery-free remote seemed very attractive.

Will your lamp test method work with a CFL or LED, or do I need to find an incandescent hulb?

ETA: So would installing a GFCI outlet eliminate the need to test for and install a ground wire? That would simplify things unless the remote switch requires a real ground. Would a GFCI “fool” it?

The model does not match the listing on the UL site:


The lamp test will not work as well with a low wattage device as you want to see if the light visibly dims on a questionable ground with increased resistance.

If I had to guess, it does not need a ground to operate. Most smart switches that people have problems with require a neutral which was not required on a switch loop until more recent code revisions. In fact, if it tries to use the ground, it will trip the GFCI as it senses a leakage.

You’re right about the UL thing. Maddeningly, this remote switch is included in the same Amazon listing as the company’s air switches, even though they are very different products. So the customer reviews and questions can refer to either type, and most often to the air switches. I didn’t think of that when I searched for the UL listing.

You said: “If I had to guess, it does not need a ground to operate.” By “it” you mean the remote switch? And that I shouldn’t install in on a GFCI outlet?

I am not an EE or an electrician. Just wondering if the sink and drain pipes are themselves metal and the sink itself thereby is well grounded ?

Y[quote=“commasense, post:6, topic:912756”]
You said: “If I had to guess, it does not need a ground to operate.” By “it” you mean the remote switch? And that I shouldn’t install in on a GFCI outlet?

I would use a GFCI for safety and yes, I meant the remote switch doesn’t need a ground. The disposal would be grounded for safety and the GFCI is an acceptable alternative.

Don’t count on that.
Even if the are all metal, there have probably been plumbing repairs/changes in a 70-year-old house – and often those involved non-metal plastic/plex piping. So that there may no longer be a solid connection to ground via plumbing.

Just for curiosity, what brand of disposer is this? Every Insinkerator I’ve put in has a 3/4” hole for a standard cable clamp to attach to. The clamp can hold a short pigtail power cord, Romex or even BX for the hard-wire option.

If you decide to go with the air switch option, avoid the Chinesium and just get the Insinkerator version at the store.

Also, you are risking, if not their life, at least the fingers of your spouse & kids with this system.

The proper location for a disposal switch is at least a one step distance away from the sink – far enough away that a person can’t reach fingers into the disposal while holding the switch. And the switch should be a momentary type – power is only on while you hold the switch on.

I know a lot of them weren’t wired this way in the past, and are still in use. As any Emergency Room surgeon can tell you. But there’s no need to install one like that now.

I’m not sure if it is code, but I’ve only ever seen batch feed units with a magnetic switch in the drain plug here in Ontario. In the US I’ve almost always seen units with a standard wall switch, I don’t think I’ve ever come across a momentary wall switch but it makes sense to me.

…“If it’s not already grounded, how can I safely ground this box? Can I run a single solid wire to a nearby pipe, and if so, how do I attach it securely?”

No you cannot. The only place a grounding wire can attach is where the pipe first comes into the house. There can be NO connections which can be removed that would cut the grounding circuit. The only exception is the water meter which must have a bond attached to both pipes so the meter can be replaced without breaking the grounding path. And I don’t even that is code anymore but you might be grandfathered.

I’m not sure what country you’re from, but that is an uncommon setup in the US, and is really a dramatic overreaction.

No one’s life is in danger from a garbage disposal. Contrary to popular belief, there are not gobs of whirling blades in the disposal. There is a spinning plate with blunt metal nubs that catch the food and fling it against an array of stationary holes or edges. It could cause lacerations or break a finger, but you are unlikely to lose a finger, and certainly not your life.

A distant, momentary switch is extremely inconvenient. Garbage disposals are a completely negligible fraction of kitchen accidents and not worth even small safety measures (aside from ordinary behavioral ones).

I am an EE.

Way back when, homes were required to ground through the cold water pipe, since it was a convenient ground and a good ground connection that pretty much every house had. Then came PVC pipe, and since a section of pipe could be replaced at any time, you could no longer rely on the cold water pipe for a good solid electrical ground. We switched to using copper rods pounded into the ground instead. But, you don’t want your water pipes to be a safety hazard, so to prevent something like a wiring short to a water pipe from making the home’s entire water system a live conductor, all water pipes are required to be grounded.

A house built in the 1950s probably still grounds through the water pipe, but that doesn’t mean that you can use your water pipes as a safety ground. There should be one and only one ground connection to the water pipe, and it should be close to both the breaker box (or fuse box if you still have fuses) and where the cold water supply pipe enters the house. I have seen a lot of cases where people have used water pipes as a ground, and it’s a really bad idea. Don’t do it. It’s not to code and it’s not safe. You want to keep the water pipes grounded so that they don’t become a shock hazard. You don’t want the water pipes to actually be your ground, except for older homes and even then you only want that short bit of pipe near the water service entrance to be used as the electrical ground, not the entire water system.

You are going to want a good solid electrical ground for your garbage disposal. If the house still has all of its original plumbing then chances are that the sink is currently grounded electrically simply because the metal pipes will physically connect it to earth ground. But as pipes age and get replaced, they can be replaced by PVC, and then all it takes is one shorted wire from your disposal to make your entire sink be at full 120 volt AC potential, with no blown fuses/breakers and no indication at all that it’s a shock hazard until it zaps someone (possibly fatally).

Romex with a ground was not what they typically installed back in the 1950s. If you can follow the wire back through the house then you might be able to tell just from a physical inspection whether or not it is grounded. If you can’t tell what it’s wired to, then you do need either a tester or a multimeter. Testers and meters are cheap.

If it’s not grounded, the proper way to fix it is to ground it properly all the way back to the fuse/breaker box. The other option is to use a GFCI, which is probably a good idea no matter what you do since a kitchen is what the NEC calls a “wet” location (kitchens, bathrooms, laundry rooms, etc, anyplace where water can provide a ground path).

So yes, use a GFCI, no matter what you do.

The proper way to ground appliances is with a grounding wire, that is connected to all other grounding wires in the house, and also to a copper grounding rod sunk several feet into the soil. Your plumbing should also be connected to this, but as ECG said, that’s to keep your plumbing safe, not your appliances.

And yes, I would use a GFCI here even if you had a good ground, because it’s in the kitchen and right next to the sink. The code does allow for appliances on a GFCI to be ungrounded, in most cases, but it’s still best practice to have a ground (a proper one, through a grounding wire) anyway.

Thanks for all the help. The job is done, and done right. It was actually much simpler than I anticipated, and if I had paid a little more attention I wouldn’t have had to bother you all.

Just before I started thinking about the task, my brother-in-law, who knows the house better than I do, had been complaining about all of the ungrounded, two-prong outlets around the place that made it hard to plug in devices with three-prong plugs. So I started by assuming the worst-case scenario, that the switch box wasn’t grounded, and was planning and buying stuff with that possibility in mind. That’s when I posted my question here.

However, once I started actually working on the job, it became obvious that the line feeding power to the switch was grounded romex coming straight from the breaker box in the basement below it. So my worries were completely groundless. (Har!)

I replaced the existing switch with a GFCI outlet, plugged in the wireless switch, and plugged the disposal into that. The wireless remote works perfectly. It’s pretty cool (and quite convenient) that it doesn’t need batteries.

After all my worries about the wiring, the mechanical installation turned out to be a little trickier than the electrical, because the existing drain hose from the dishwasher was 1/2-inch i.d., not 7/8, which the disposal needed. But after visiting two hardware stores I found an adapter that I was able to modify and make work.

Thanks again for all your good and informative advice.

Why not just fish a grounded cable to the panel? It is usually not that big a deal. It may require a small drywall patch somewhere, which really is not as big a deal as people seem to think either.

Yes, I know, you don’t want to bother with an electrician, but you probably should.

Didn’t read my last message? :grinning:

A new wrinkle. I had connected the (fifty-year-old) dishwasher to the load terminals of the outlet, and after running it the first time discovered that something about its final drying cycle trips the GFCI. I’m going to run it again, to make sure, but even if it doesn’t trip again, I think I’m just going to move its leads to the input side of the outlet so it’s connected directly to the breaker, not through the GFCI, to avoid future problems and confusion after I leave. The disposal will still be protected, which is more important, and the dishwasher will be status quo ante.

Any reason not to do that?

Just to be sure: Is it a GFCI (ground fault circuit interrupter) that you have, or an AFCI (arc fault circuit interrupter)? AFCIs can have false positives, especially for things with motors in them, and so are not recommended for all applications. But if a GFCI is tripping, there’s a reason for it, and something is wrong with the load on it, something likely very dangerous. If a GFCI is tripping, you don’t want to just bypass the GFCI. You want to find out why it’s tripping, and fix it.